Regarding asking the CG office for permission to trim a limb ... one night during a storm in a CG, a large (dead) limb in the empty spot next to us fell and could have done serious damage to our RV if we'd been in that spot instead. If the CG owner had been "keeping up" with trimming, it wouldn't have happened.
If I didn't like the look of limbs before backing into a "private" CG site, I'd go to the office and ask permission to cut.
In a "public" CG (county, state, federal), I'd just cut limbs without permission in order to keep from scratching and/or otherwise damaging our rig ... but I would place the trimmings in a place so as to not bother any other sites or bother general campground ambiance.