Hello! We recently got a lightly used 2023 GLE for the wife. It was very reasonably priced and had all the right options except for 19” wheels - which IMO look too small on the car.
So I am looking to replace them with a used 20” set. My question is: will this be a simple swap or do I have to worry about other issues such is wider fender arches etc?

 

There should be plenty of 20" OE options that simply bolt on, but since the base 19" wheels have a smaller diameter than the optional 20's, your speedometer will be off by roughly 6%.

 

Not only do the wheels look undersized, the OEM 255/50-19 tires are almost 2" smaller OD than other options. You should be able to find 20" take-offs. There is also the option to upsize the tires to 255/55 or 255/60, which does not solve the wheel problem. As HotRodW says, there will be some speedometer error when you go larger OD.