Well if BTC goes up, certainly the altcoins will also go up in USD yet its satoshi price will drop as well. Anyway, if you are patient enough you will experience its bullrun, TRX is not going to make you rich but it's good only if you want to gamble. Its where it had found its purpose because of the cheap transaction fee and more apps developed under it are casinos.
Not necessarily, sometimes alts do lose a bit of value during Bitcoin rallies. I always felt this was because people would let go of alts and go into Bitcoin to enjoy the rise, then buy back alts when BTC is strong. I do not know if this decoupling is getting stronger in recent times,,, but it definitely seems better than in the last rally.