Just wanted to add my thoughts as I'm looking at 20x10"/11" rr or 19"x10"s rr on my other vehicle soon.
265 mm tire widths, with a 50% aspect ratio should really fit a 9.0" rim for maximum performance. The "European performance-look" would be P265s on 9.0" rims. 8.0" stock is too narrow as you can see by the way our P265/50xR20s sits at 32psi cold. Even over-inflated @ 40+psi , the sidewall still doesn't sit flush with the rim as it bulges quite a bit. Furthermore, the OEM contact patch is wider than the OEM 8.0" rim. Compared to nearly flush tires (perfect look imo) at 215mm on the common 7.0" rim we are lacking a lot of wheel for P265s even though the FX is an SUV. 245s match 8.0" rim widths excellently with a ~ 1.6" greater tire width (sidewall edge to sidewall edge).
20x9.5" wheels are great wearing P275/285 (285 ideal) and 20"x10" wheels with P285 & 295/xxZR20s (295s ideal) with the proper aspect ratios. We're talking about best dry-road performance with minimum sidewall flex and best "look." Of course, you need the proper wheel offsets to match wheel width when upsizing. Aspect ratios will then help you determine a compromise between ride quality, sidewall flex, the look you like best and handling trade-offs beyond the discussion of tire widths alone.