Alright then, we got an upgraded version of chompers to deal with, so following the advice of Sun Tzu, let's first know our little enemies before worrying about any battles and see exactly what they do:
1-intelligence: this is by far the most important thing to check, because how intelligent an animal is directly impacts how capable they are of problem solving and escaping traps and enclosures. Your ploppers are twice as smart as ravens, but how smart is that? Well it's actually pretty smart. Ravens can organize themselves in groups, hold grudges, plan ahead and have demonstrated to be on par with adult primates regarding performance in certain intelligence tests. Then what does it mean to be twice as smart as a raven? I'd say it wouldn't be that absurd to assume your ploppers are as intelligent as some early hominids, possibly as smart as a young Neanderthal or even a young human. What does this mean if it's an accurate assumption? It means that if you want to involve tactics like traps you'll need to understand you're not really dealing witha group of weird animals, you're dealing with an organized group of fast critters with potentially near-human levels of intelligence that can climb walls and spit an acid that reacts violently with organic tissue. That comes to show how much of a threat they can be, especially if they don't see humans as a threat they can't overcome. THAT WOULD BE if their nervous system wasn't decentralized, because that means it technically shouldn't be all that smart since there isn't really a cluster of nervous tissue to really specialize into a more capable brain, but because it's a magical monster I'll just mostly shrug it off and still assume it's a little dumber than your average human.
2-durability: this part was elaborated well. They can handle some fairly heavy blows, stand on a fire for short periods, are immune to any attempts to drown them.
3-mobility: these are some speedy boys, since they can out-sprint Usain Bolt as well as most humans in a normal sprinting chase. The fact that they can also sprint on the ceiling and on walls due to the snail slime means that they're probably hard to catch, especially within an enclosed space where they can just go to the ceiling (and vomit acid on you from there). This speed and climbing ability also means that, if they produced it at a fast enough rate or were able to control the output, which I assume they can to a degree, they could easily, due to their intelligence, just go to a higher ground and projectile-spit acid at exposed parts of humans targeting it, simply skating away to to safety if someone came too close (monkeys know how to throw rocks and understand sometimes they can reach places others can't, so this is far from an exaggeration). However, I don't think the egg-shaped thing with 4 little legs can jump well, so I'm fairly certain that if they want to go somewhere higher, climbing is their only real way.
4-offensive capabilities: like I already spoke a bit about, their acid attack is probably one of their best weapons, since their ability to climb surfaces and intelligence allow them to better exploit its potential. Other than that thigh, the only other attack options I see include variations of charging at a human's lower leg or biting them with their chomper mouth, both of which require getting very close. Sure they could potentially climb a person and give it an acid bath, but it would probably require it to use a lot, if not all of its acid reserves and thus would leave them stuck with their significantly less dangerous attack options until they produced more (yes they have a large mouth but it won't do much when you're the size of an elephant bird egg that can easily be grabbed by a person when you get too close, and before you think the slime would make it Hard to hold onto, they have 4 arms that end in egg-shaped orbs, so not as hard to hold as you'd initially think). These orbs could also hurt a bit if they were to use them to hit an enemy, but this is by far their least effective offensive maneuver, and most likely not something you'd normally see them using unless they've completely ran out of other options.
5-numbers: you said that 90% of all chompers that eat plops become ploppers and that both chompers and plops have populations comparable to rats in the wild. Now the problem in this is that 1-I couldn't find any exact numbers for what exactly that means and 2-in some wild places rats are an invasive species which multiplied absurdly and caused many problems to the ecosystem. Based on this it's hard to estimate, but I'd say there's a fair number of ploppers roaming around, which is a big problem due to their intelligence and potential to work in groups.
Summing up what we got from this analysis, if say that your poppers are a less capable, slightly less dangerous, less abundant and MUCH more family friendly version of the goblins from the show Goblin slayer. They're present in large enough numbers to be a threat but lack the necessary structures to become a more meaningful threat, like grasping appendages for tool use, being stuck with whatever they can manage with their natural abilities.
Threat level from S+ to F-: B-. The only traps they can really make involve luring you to a place where many others are waiting to gang up on you and give you an unpleasant acid bath. They can't use tools and can't jump out of the way, but their intelligence still makes them hard to trick and able to both plan ahead to a degree as well as hold grudges if you let one escape. Their main attack is clearly their acid attack, still don't think they're totally harmless. Not only they can still pack a mean bite if they manage to align their bodies properly, they can easily skate out of the way and away to a more strategic location. Their fairly large numbers also make them troublesome due to the fact that they can and likely will form, travel in and hunt in organized groups like you see in chimpanzees.
Now that we have analyzed the enemy, how do we prepare against it? Well if my comment has given any hints, I'd say the best strategy to fight these things include making not some omelets but some boiled eggs. If there were enough resources my strategy would be pretty simple:
Step 1- make a fairly large (preferably 7 to 8 feet) and decently deep moat around the entire village and preferably line its interior ground and walls with uneven rocks, including drawbridges for people to enter and leave. This combined with high enough walls makes it so ploppers attempting to attack the village must either enter the moat or use the drawbridges since they can't jump over it. Problem is that if a plop falls inside the moat, chances are they can't really get out, since their slime doesn't really work as well underwater and the uneven walls of the moat inhibit the use of their suction cups. This alone should already help you deal with invading ploppers, since their lack of tool using ability only gives them the option to dive in or to leave.
2-if you find a plopper stuck in the moat, get a group of metal boxes, use 8 feet long rods with a basket at the end and use it to remove the ploppers form the water, throw it in the metal box and close the lid. Poppers are smart, but without contact with the ground they're not very mobile and they have little to do to prevent this from happening. Carefully lock the boxes and use ropes to drag it to the proper place.
Step 3- light a big fire, toss the metal boxes in it. The ploppers will boil and cook within the box soon enough. After that, wait for the boxes to cool, open them up, take the dead plopper and hang it near the places with the most plopper activity or near where it was found. They may be smart and able to hold grudges, but they're also smart enough not to target the village that regularly exposes the corpses of those who get too close.
Like SirTainsaid, they might be very troublesome foes and even be an actual danger to someone unprepared, but they live in a world where humans exist, which means that the magic that spawns the 2 creatures that create them is the only thing truly keeping them from crossing with humans in a hostile manner without ending like the wholly mammoths. If they're really as smart as an hominid, they'll learn in no time that the hairless monkeys they attacked a couple times also hold deep grudges, and that avoiding them is always the smartest thing to do.