Can anyone list the wheel offset versus size for the E21?

If there is a 15x7 wheel what is the required wheel offset?

17x7?

I have some VW wheels but there all 17x7 and +45mm.

For 15x7's, et12 to et15, et20 may work with some wheels.

For 16x7 and 17x7, et12 to 15 will be best but et25 will fit because the larger diameter will clear the front tie rod ends. You'll need lug studs and 20 or 25mm spacers to get those to fit.