If someone asked me this same question today, this is how I would answer it with my current understanding:
Consider what you’re actually trying to train, and then isolate that and train it. Don’t try to train too many adaptations in a single exercise or workout. Especially for max strength/power training, whatever fails first is what is getting the primary stimulus.
For example:
If you want to train maximum grip strength on tools, then do that. This means dead hanging without the pinkie rests in order to require maximal gripping force which results in maximal strength adaptations in the grip muscles. Don’t think you’re going to get max strength adaptations during technique training or body tension training.
Full body twist-locks on a steep wall will most easily target strength/power in the larger pulling and core muscles specific to climbing, if done on large enough holds or tools. Whatever fails first is what will get the primary stimulus, so use good enough holds that you can hold on for the full length of each rep.
Use moderate to intermediate difficulty routes to practice good climbing technique, including time spent on technique drills. During this time, focus on climbing efficiently, smoothly, and without a pump for as long as possible. This will include holding on to the tools as lightly as possible to stay attached, and taking advantage of the pinkie rests. Keyword: PRACTICE – not training. Though this volume will contribute to local muscular and global aerobic capacity if you keep your heartrate/intensity in check, and the duration is long enough.