IDK if this helps you.. I'm running 19s with front 8.5 et15 and rear 9.5 et22.. Rubs when I have more than 3 passengers. My car is also lowered.

Lamda28 ,you need to give your tyre sizes.

Forgot to add....tire size, which would be the OE size....

245/35 front
275/30 rear

According to the site I was looking at with the above wheel specs listed, it said 100% fitment for my car. I'm just curious if they would stick out past the fenders. I really don't want to have to worry with rolling my fenders later if I decide to lower.

The offset calculator link above said

front: 4mm less inner, 8mm more outer, compared to front 124s

rear: 29mm less inner, 9mm more outer, compared to rear 124s with 15mm spacer

The front is ok, you could even use 5mm spacer there.
The outer edge of the rear wheel will sit exactly in the same point as mine (8.5" ET14 + 12mm spacer) and it doesn't rub. I can't tell about the inner edge though.

5mm spacer in the front

10-12mm spacer in the rear...

For a 275mm width tyre,the recommended rim range is 9" to 10".It will look a bit stretched on a 10.5" rim.

What would be the correct tire size to fit the 10.5" wheel?

you can stretch a 275 width tire. usually we would put a 285 width tire.

so a 285/30 then?

Still trying to decide........

Will a 9.5 et33 fit up front? According to the calculator they will only extend out 6mm further than the 124's, but gives you 32mm less clearance on the inside.
Is there enough room for that? Other option for the wheel i'm looking at is 8.5 et15, but that extends out 11mm further than the front 124's. Is that too much? I want them to be flush or slightly recessed/ tucked on the front. Def don't want them sticking out!

For the rear, I think I've decided to go with a 19x11 et33 which extends an extra 9mm over the 124's with the 15mm spacer.