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.
I think it resembles cars a bit. Think about it this way, you are in a car, and it is not working, you start and put the pedal to metal and start as fast as you can. Normally you yourself go a bit back right? So for a fraction of a milisecond car did moved ahead but you moved back, obviously it is very very slow but there is that incredibly tiny moment that could maybe not even be cathed on camera you are further behind (by milimeters) then where you started whereas car is a bit (milimeters) further ahead. Then you go ahead with the car and both of you go further.
I see it similar, bitcoin goes up, altcoins prices stutter for a second but then they all go up as well and catch up with bitcoins increase. That doesn't mean that we should not be hoping for altcoins to drop, that just means that we should not be worried about bitcoin going up and altcoins going down.