Don’t be afraid to get in there with some snips and open up some breathing room for the new shoots. Bending a few older shoots to get to the crowded sections won’t really do too much to hurt the plants while they’re dormant. There’s a reason so much information about bamboo is how to get rid of it - it’s very good at surviving. To add to that, if your plant is dormant for the winter, then almost all of the plants’ energy is in their roots until the signals are there to push new growth.

Speaking of roots - winter is a good time to check your plants for any signs of being rootbound in their pots. If you can, try to shimmy the whole root ball out and see how much unoccupied soil is still in there. If it’s roots all the way down, you can safely remove about a quarter of the root mass before replanting them (it’s totally fine to sift out the roots you’ve removed and reuse the soil). Doing this will keep them from strangling themselves, which can happen to any plant left in pots for too long (it can happen other ways too, but that’s not really useful here). Use a sharp knife or shovel - no use damaging more than you intend to - and disinfect your tool of choice in between plants with alcohol or bleach to prevent transferring any disease that might not be observable. That goes for what you use to cut the growth above the soil line, too.