Purely building muscle---How to lift?

What's up guys!

I am kind of confused as to how I should workout, since there are different ways for different goals.
My main goal is purely building muscle, and I do not care for strength gains at all....Shocking I know! But due to certain injures I'm unable to do two major compound exercises, but that's a long story.

I ask this because on the bench press I can take 200lbs and reach failure on the 10th rep. And then If I lift half that weight but focus contracting the chest, I reach failure on the 10th rep as well with 50% of that weight, only this time my chest is fatigued and pumped versus before when I hardly felt the muscle.

But when I lift without focusing on the muscle, I can progress in strength much faster than when I lift focusing on the muscle, which has a slow strength progression.

My question is for purely building muscle should my reps be done in a slow controlled manner, really focusing on stretching the muscle and contracting it? Or should I be lifting in a power lifting manner where I lower the weight a bit faster and try to explode up without much thought of the muscle, with good form of course?

Thanks!