Does exposing lower bud sites that were previously...

* never cause a gap in canopy.. light missing leaves is useless and light hitting anything but leaves creates significantly less ATP, the important product of photosynthesis. A currency for building block creation, i.e. growth. Sufficient ATP production is what causes better buds deeper into canopy. like i said it is very mobile. within the plant. It's readily available throughout phloem.

nope, and if you reduce total energy absorbed by plant in any way, it only reduces your overall yield. A little circulation, a little decongestion can help in some contexts but never create a gapein canopy. Light hitting leaves is the key, not bud sites. ATP is very mobile, but the plant will always favor physically higher nodes, aka "apical dominance." The plant will absorb all the energy and dsitribute it. if you did well taking off "suckers," it should be a vast majority of good buds. When you leave too much underneath, you get some larf which is great for hash, extracts, rosin, edibles et al... too many colas will reduce bud size too and potentially lead to higher proportion of larf. I just made that mistake, lol. Gives me a good reason to press some rosin. cocoforcannabis has an awesome article/post on this subject. it is well-informed and well-explained. dr photon's corner or whatever, should be easy to find with a little browsing. worth a read.

No, not really...........this is why I believe defoliation is (mostly) unnecessary.

It's not gonna make stuff that's at the bottom turn into top branch buds but allowing your light to penetrate deeper into your canopy will make a difference, assuming that it's still within your light's range of "useful light". If it's too low you're better off removing the shaded growth so energy goes to better quality buds.....unless you keep your larf for concetrates/edibles. It also needs to occur early enough in flower to matter. Cleaning up your plant a week before harvest isn't gonna mean much.

Yours are all exposed, i am in trouble . And yes, even big branch top if heavily shaded by few leaves above is not developing well, so selective defoliation is needed. I choose to clean bottoms and leave a foot of green mass depth. Then few leaves here and there , trying still to keep all mass. What is shaded for human eye is sometimes not for plant, dont make holes in canopy, bend, tie leaf if needed, tuck it, but try to keep. My view. Good luck !