I'm writing a neo-pulp adventure and one of the planets that appears needs to have the following characteristics:

• Is populated by giant non-sentient non-humanoid insect-like aliens, some from the sizes of cattle but some from the size of a Boeing 747. Some of the bigger creatures should be able to fly.
• The atmosphere is very thick and most of the planet is very jungle-like like a rain forest.
• The flora is not so Earth-like, there are no trees, but plants with flowers can grow taller than redwoods.
• There will be one type of spider-like creature that creates something similar to a spider web but strong enough to capture a small flying vehicle. Thus this creature should be able climb plants.

Now I was thinking that for many of these characteristics it should have lower gravity however I'm not sure if is physically possible for a rocky planet some N times Earth's size to have lower gravity. I know that a planet's gravity has to do also with density and not only size, but again, not sure if a rocky planet can not be dense enough to have lower gravity than Earth. Another possibility is to make the opposite, a planet with high gravity with its fauna adapted to it, however in that case I doubt flight will be possible.

Keep in mind that:

• Earthlings (as I'm not using the term human) are not going to stay there for much longer, just a couple of days, weeks at most.
• If Gravity is higher than Earth it should not crushed humans and human-size aliens that arrive there, but can cause some discomfort.
• Technically is not necessary for it to be a super Earth, even an Earth-size planet is still huge but if possible to keep this will be more fun.
• Is preferable that the atmosphere is human-breathable.

Thanks in advance.

PD: Is a neo-Pulp novel so is certainly not hard sci-fi, science doesn't have to be rigorous (although some scientific accuracy doesn't hurt anyone) but the point is it's soft sci-fi as long as avoids magic or fantasy explanations will be enough.