I've really liked hitbox controllers for Street Fighter 6. I've been really happy with how they've turned out and they're a joy to use. If there's interest I can post the build process/instructions/guide.
Also would be good to grow the community if you're interested: !arcadesticks@lemmy.world
Any layout will come down to personal preference and the best thing about making something completely DIY is you can customise it to your liking.
The layout I made was the standard template most controllers use now and I wanted to stay close to that so the muscle memory easily carries over to using other controllers. Frankly, I don't find it interferes much with reaching LP or MK quickly. I tend to rest my fingers across the upper row and come down as needed for kicks.
Resting the hand on LP and MK would make an odd position for twisting to get to other buttons. Also it would put the pinky finger farther away from the drive impact shortcut (right most upper button).
For anyone planning to use a hitbox controller I'd recommend printing the template on a page and seeing how your hand rests and if you want yo change button positions. Or if you've ordered the buttons then I'd recommend cutting holes in a cardboard box to test fit your button layout and test what you like. On the upper controller in my picture I've moved the jump button further down so it is more comfortable under my thumb.