Basically, yes. What you want to snip off is what some people call suckers, the new growth that eventually becomes new branches. There is a plethora of info online about this and I’m sure most can explain it better than I can.

For the one you don’t know if it’s worth saving. Start by cutting off everything dead or dying. Try not to worry about killing it, plants are usually more resilient than we think they are. Plus, if it does die, you can always clone from the other one.

A real life example for you. Last year I attempted to trim back a bush in front of our house. It didn’t go as well as I had planned and I said fuck it and took it down to the ground and got rid of all of the green on it. It’s now a much smaller version of itself but it’s doing well and this year I can do my best to guide it’s growth and keep it trimmed back and less of a pain to deal with.

A thought. With the little room you have to work with, you should maybe put some of them in hanging containers or throw up some shelves.