I would personally lift or level it before you put wheels on it. The biggest tires you can put on a stock height ranger still look small in my opinion. I’d lift it to get some clearance for bigger tires. I have 17x9 +12 offset wheels with 255/80/17 (33s) with a 3.5” lift. The tires fill out the wheels wells nicely and it looks more proportional.
My wife’s Ranger has a leveling kit. I put the same size wheels with slightly less offset and 265/70/17 (32s). I think those are +25 offset? Can’t remember, they’re about 1/2” less offset than mine.
Worth noting I had to remove crash bars on my truck to get tires to fit without rubbing at full lock. Her tires have about 1/2” clearance so I didn’t need to remove the crash bars on her truck.
Most important thing is do what makes you happy dude!
I am running some 18x9 -12 offset wrapped with 285x65R18 Falken wild track. Factory height, I am rubbing on the mud flaps. I would recommend a front lift of 1.5inch to level the truck and you will clear the mudflaps.
Why 20" wheels on a Raptor? The less sidewall height you have, the less performance you have offroad and the more prone you are to wheel damage. Unless this is a mall queen only driven on the street? No offense if it is.