Depends on the offset and spoke design. Many 18x7.5 wheels will not clear 6-piston calipers (e.g., Brembo). You usually need an 18x8 or 18x8.5 for large brakes.
The 7.5-inch width is one of the most common rim widths for modern sedans, crossovers, and sport compacts. Why? Because it sits perfectly in the middle of the tire compatibility spectrum. 18 7.5