offset understanding with air suspension in the future
 

Hey guys,I'm learning here. I'm looking into wheels, tires, and air suspension. I'm stuck on wheel size and how to choose the proper size. end game is wide tires that can still fit in the wheelwell once i lower the car. so I'm stuck with what i can fit in the wheel well and be wide. i would like 305's in the rear and 275's up front. what offset/backspacing is the maximum/minimum with still having the wheel and tire fit in the wheel well once lowered. how can i figure out what the minimum/maximum measurements of what can fit? any explanation or link to literature would be appreciated. id like (front)19x9, 275/35/19 (rear) 19x10.5 305/40/19

thank you!