Either way man. Isn’t T25 mostly calisthenics with a resistance band thrown in here and there?
The cool thing about doing progressive calisthenics while you lose weight is that your body will be used to doing the exercises with the extra weight so you’ll be even stronger when you lose it.
Overall I’d say it’s probably a good idea to do both until you lose the weight, then you can cut back on T25. T25 relies on little to no rest intervals to get a good conditioning workout. This is great for burning calories, building endurance, losing weight, etc. But for building strength it’s best to recover longer for more recovery so you can continue with maximal strength.
Actually strength training calls for a lower rep range than muscle building. Muscle building is like 6-12 reps a set but strength building is under 6. Just make sure the exercise is appropriately difficult. Set numbers should be the same. 3 days a week is a pretty good frequency though, although once you get used to doing difficult exercises frequently you can do it more often. Meanwhile that approach may not be optimal for muscle building because your muscles need a lot of time to regrow, whereas with strength training a lot of it is neuromuscular recovery, which doesn’t take nearly as long.