I use a wide grip for bench and have a fairly developed chest. I struggle to get the bar into a good position for lowbar, but don't want to widen my grip as I find I get better tightness with a narrower grip. As a result, I've been experiencing bicep pain during bench due to, from what I understand, strain during lowbar. Luckily, this is mostly because I've been running smolov (squatting 4 days a week) and I don't typically experience pain. In the long run, I think it would be better however to improve my mobility. I've been doing shoulder dislocations, and tried to stretch my chest more but I still lack a lot of range of motion. What else can I do?
If you are having trouble getting into a comfortable position, there are two things that it can be. Morphological (i.e. your body structure prohibits getting there), which there isn't much you can do or flexibility. Since you've indicated you have a limited range of motion (ROM), I am working on the theory that your muscular development is limiting the mobility.
If that is the case, there are quite a few stretches that you can do, and most of them come from the swimming world. The old (1970'-early 1990's) traditional swimmers stretches have been mostly deprecated, as many of them simply weren't good for the shoulder capsule and led to a lot of shoulder problems later in careers/life.
There are many different approaches, so I would sample some of the below referenced stretches, and find what works for you. I would also suggest that you look at overall upper body mobility (so lats, traps and so on) rather than just the area around the shoulder itself (SITS, etc). I also would recommend you look at the "don't do this" part of the first linked article, as those are the stretches that are being eliminated.