I sure you guys can help me. I’ve always wondered about how switching wads of the same style in a load affects things. Example, taking a published 1 1/8oz load calling for a waa12 and loading 1 1/8oz in a waa12f14 for that load, 1oz load using a waa12 in place of a called out waa12sl,etc. I know it may effect the crimp but other than that how much if any does it change pressures and fps? I patterned the difference long ago with good results as I remember. I’ve shot a ton of 1oz loads out of wt12’s with good patterns and my old backline trap load was 1 1/8 #7’s in a waa12f14 but this was just from advice of an old timer. And I know published load and all but I don’t recall ever seeing such a thing published. What are your guys thoughts?

I've used WAA12F14's for 1-1/8 oz. loads with 18 grains of Red Dot and a Win.209 primer in a WAA-HS hull, I'm sure it was just a replacement for the WAA12 wad, it fits in the HS nicely.

Ive pretty much settled on using the next size larger Capacity wad for WWAA HS. Got to do that or stack height isnt right (here for me)
That applies to me specifically 7/8oz shot load with claybuster wad [have to use the wad for 1 oz shot]. Other wise the HS hull gets a "wrinkle" in it squashing the load and forcing the 7/8 size wad to fit using 7/8 oz shot.
If your original question was IS IT SAFE to swap wads?, I never give it a thought safety wise. Mostly because my loads are in the mid range pressure wise, and its just common sense.

For typical target loads of 1 1/8 oz. and less, in a 12 gauge, using a wad with a shorter compression section usually does not change things all that much.

I would not assume the above to be true when you get to heavy loads with the slower burning powders.

What the OP suggests is common practice for adjusting stack height using bulky powders. What powder are you using? There are wads specially made for use in the AAHS with bluly powders, the DRA12.