Hi, New here.

Frankly, I've been asking questions in other forums but feel like I've asked enough newbie questions. Kind of embarrassed at this point.

I hope I don't wear out my welcome asking things I really don't know here.

First one..

I have a 60x32 kerdi base, but my opening is 56" meaning I would need to trim 2" of each side of the base. When I hold a level over the 2" of preslope I need to cut off, I see it would be less than 1/16 lower than the uncut sides. Is this a big deal? Do I really need to cut the base narrower than 32" for a consistent height all the way around?

Thanks

You have two choices: modify the base to get a level perimeter, or modify your first row of tiles to get a level first row. It's about the same amount of work either way and no one will notice the difference.
If it was me, I would modify the base, as it makes the rest of the job flow better. If you want to preserve shower size, then cut the two sides, and the back evenly and then fill in the curb side with 2 inches of topping mix concrete. The curb side does not have to be the same height, since you will be cutting those tiles regardless.

Personally, I would cut the tray to fit and leave it. You can shim up the wall tile to make them level considering it's less than 1/16", especially if you put the floor tile in last, as that would cover the bottom edge of the tile anyway.