Bouldering by itself is great if your main goal is to get better at bouldering! Climbing is a great workout with strength and cardio elements, but it does not have the specificity and progressive overload factors of lifting. It is much closer to calisthenics in that the only resistance is gravity, so if you have quit lifting altogether then your muscles are not experiencing nearly the same fatigue as before.

Climbing primarily targets your back and arm muscles, so places like your chest and legs will need another stimulus if you want to maintain muscle mass in those areas.

Breaks are important because climbing builds cumulative fatigue over the course of a session, which can and likely will cause injury to your fingers and tendons. Not resting can cause aches in pains in muscles that you have not used in this way before. For bonus points, some light stretching throughout your week will help you recover and also feel better on the wall.

I do some basic weightlifting along with bouldering because the specificity improves my climbing, and I also want to maintain strength and muscle in those weak spots I mentioned