Someone who played at the recent preview mentioned that you actually cannot curve your punch after thrown. The curving is only done at initiation. If that is true, that means you cannot simultaneously move and curve your punches at the same time anyway.
From the demo event I played in February, this is false. I think it depends on the arm you are using, though, as certain ones (like the Boomerang) feel noticeably more flexible mid-punch than others. We'll know for sure in a few days, anyway.
I've only ever considered playing this game with motion controls as that is what sold me on the title in the first place, but the one aspect where it may be a bit cumbersome compared to the non-motion schemes is character movement. Tilting the sticks to move was difficult to get used to and felt slow, to the point that I found myself wishing for a hybrid dual Joy-Con scheme with stick movement and full motion punching. But it may just take practice, and perhaps the game is balanced such that movement doesn't matter nearly as much as the punch/guard/throw interaction.
I'll probably try the non-motion scheme just to get a handle on it, but my sense is that if I'm in a public place where I can't flail my arms, I'd rather play a different game entirely.
It will be interesting to see if there is a visible tell that your opponent is using a non-motion control scheme (from carefully observing the movement and the punches), and whether a distinctive counter that punishes it emerges in the metagame.
