Wheel size/offset?

[ClemsonVQdude]

I know there’s a lot of threads on this and I know about the wheel fitment calculator and all that but I need an answer for my exact situation, i have a 2013 370 base model, so that’s
front - 225/50/18, 18x8 +43 offset
Rear - 245/45/18, 18x9 +15 offset
Correct?
So, I have 1.5 inch spacers in the back and 1.25 inch in the front, I’m wanting to go up to 245/40/18 in the front and 275/45/18 in the back and also wanting some concave aftermarket wheels. Im not exactly sure how the whole offset thing works and how the spacers affect it, what should I be looking for in a wheel in terms of width and offset for it to look right and not throw everything off?