I think a one knee stance will limit lateral mobility at least one direction.
It depends on your pitchers command I think. Blocking might be a bit overlooked but I listened a podcast with a Dodgers catching coordinator and he said it is basically like this: if you block it nobody will give you credit but if you let it pass you will be blamed.
Sure the focus is more on framing but balls to the backstop are losing games quickly. The focus on framing is due to catchers skill in blocking and pitchers command in mlb but one thing is sure:
No matter how good you frame, hit or throw if you have balls going to the backstop regularly you are not catching long because nothing creates are many runs as passed balls (just watch little league games were like half of the runs are created via balls to the backstop).
Yes framing is the big thing and if you are confident you keep the ball in front of you then go for it but nobody will thank you for the strikes stolen with your framing when you had 3 passed balls and 4 runs scored with them, especially since there is no pitch fx in amateur ball.
Those catching videos today are all talking about framing but most amateur coaches are happy to have a catcher who is decent with the bat and who keeps the ball in front of him because if you pick up the ball behind you after it bounces from the backstop that means trouble.
I'm not saying you shouldn't try to frame but overall you get just less credit for your framing at the amateur level but blocking plays a larger role because pitchers have less command and catchers are also worse at blocking.
I'm not really a catching guy but I know that passed balls are losing games and coaches will have very little patience when they happen.
Now an occasional PB is ok but you have to get that not giving up runs on passed balls is your first priority.