I find the best combination is just to climb on rock as much as possible and supplement it with pure training (fingerboard, core etc.) and just forget about indoor bouldering. Climbing on plastic doesn't seem to make me any better at rock climbing or be that practical for working specific physical weaknesses.
At my lowly punter level (7a), I’ve found bouldering indoors extremely helpful at improving my sport-climbing standard. However, my self-diagnosed primary weaknesses - lack of power and a trad. climber’s static and front-on climbing style - can be effectively addressed on plastic. The other consideration is logistic: not everyone has ideal access to climbing on real rock.
The OP probably doesn’t need any advice from me, but might not some specific-to-angle and hold-size 4x4s or similar be of use?
