I ask a lot of questions in my answer not so you can answer me or give clarification, but so you have ideas and know what to think about when writing your story. Please don't disregard my answer for that alone. Anyhow...
My first thought would be to make these faster zombies short-lived. If they are fast, this means that whatever made them zombies has avoided most of the muscular (and probably skeletal) system. Because the pathogen hasn't impacted their movement and metabolism as much as normal zombies, they burn more calories, are more active, and therefore go through more wear-and-tear than traditional zombies.
A faster metabolism also means that these zombies need to consume more to maintain their energy. Naturally, this means they are more susceptible to starving, and would have to consume far more nutrients than a traditional zombie. And since they're zombies, perhaps whatever made them zombies also impacted their body's natural ability to analyze fat cells and the body randomly starts breaking down random pieces of flesh for energy (giving you an explanation if you wanted the traditional "bones showing through ripped jeans" look).
You mentioned that the zombies are afraid of water. There are a couple variables you can play with here. For example, whether or not they're afraid of small amounts of water, like a liter, or if it requires a larger amount; if they're afraid of blood (more on this later), etc. There are other hazards that need to be considered as well, such as fear and damage from fire, sunlight, impact/puncture/slashing damage, sounds, general light, etc.
So, blood. Zombies being afraid of blood opens up all sorts of possibilities. The first thing that came to mind was the potential of the survivors cutting themselves in order to release blood to scare away the zombies. This has all sorts of repercussions, like infection (especially to zombification), wasting of medical supplies, permanent physical damage preventing future escape or defense, psychological repercussions (and they, too, would eventually become numb to pain), etc. And do the zombies fear their own blood (if they have it), and if so, how does this affect feeding?
Now, the others focused primarily on what makes these faster zombies weaker than traditional zombies. But first we have to decide what makes them stronger, as well as what makes zombies strong in the first place.
Zombies often have strength in numbers. Hordes, mobs, gangs--whatever you want to call them--of zombies are much harder to defend against than a single or a handful of zombies. This pack mentality is a strength in that they know to gang up on survivors, but is also a weakness since these zombies fail to analyze their environment or formulate any other "strategy". Against hordes, limitations are mostly limited to marksmanship, ammo, strength/energy, fatigue and means of escape. A fast horde merely makes all these factors more important.
Next I want to talk about durability. Exactly how much damage will your zombies be able to sustain before showing signs of weakening and eventually defeat? Will a headshot limit their motor abilities (or even kill them), will damage to any part of the body limit its use, and how much can they heal after "battle"? That last one is a big one I don't think many consider. Strategically, how much of their resources will the survivors put in to defeating zombies they meet in order to prevent them from coming back to get them? And if the zombies survive, will they be able to tell other zombies the survivors' location? (like how ants and bees can alert others)?
Now, processing and computational ability. Just how much can zombies learn, analyze, perceive, process, etc.? Can they measure danger, and retreat to save their own lives? Do they even have instincts to survive, and if so, how much (and why would they go after humans if it means certain or a high chance of defeat (if they can think that much)? Before I mentioned a pack mentality, and psychology is a far overlooked element in zombie literature and media. Do they require others to process information and make decisions? Are there alpha males and beta females? Are there even genders? Is there a hive mind, or does the pathogen give them new instincts to go on? Do they have families, friends, relations, etc.? These can all cause strife on their own. Examples: a renegade from the hive, conflict for the position of alpha male, political events and political power, alliances/factions, etc.
How is the virus spread? Is it airborne, intravenous? Does it use living vectors, like plants, natural bacteria (like the ones we have on our skin; this a big one, because if so, there's not much way to avoid it for long), or through asymptomatic/immune carriers (like a seemingly uninfected bird or dog)? Are they afraid of water because the pathogen can't spread over water?
You mentioned various kinds of strains, and I would like you help you improve upon that. Assuming you know how the pathogen can spread, what if there were certain forms of zombies that acted like infantry and ran only to spread the virus (like suicide bio-bombers)? Plants and fungi are crucial topics. Can they spread through root systems and mutate the plants, creating spores or poison? Can they sense and communicate through plants?
If you want fast zombies, perhaps they're just animal versions of these zombies. If the virus can affect multiple species, you could just have different variants that depend on the species, like air-bombing birds and espionage squirrels.
That also brings up the topic of pets. A pet is another mouth to feed, and one requiring special food, but have superior abilities. They can alert the survivors to zombies using their superior senses. Birds can deliver messages (if they've traveled a route previously and are trained) and can do "reconnaissance". Dogs can attack as well as scavenge for food, as can cats. Perhaps reptiles and amphibians are immune to the virus (antidote, anyone?). Pets can also provide psychological support, which is direly needed in a situation as damaging as this. Remember, power is not just in destructive capability but in all results that can be achieved.
I might add a little more after submitting, since this was a very long-winded answer. But I had a ton of fun writing it, so thanks!