USA=GLC43=all-season tires=130mph top speed
 

So, read the all-season tires mean the GLC43 Coupe comes with an electronically limited top speed of 130mph.

If I opt for the 21" wheel upgrade versus the standard 20" wheels, will the 21" comes with summer tires meaning the electronically limited top speed of 130mph is increased??

I know this isn't an issue for most of you, but occasionally it's nice to be able to go over 130mph in controlled, track conditions, etc..

If you're the type of driver that thinks he needs to go over 130mph, then you're likely the same type of driver that would purchase an ECU tune. An ECU tune will eliminate the top speed limit.

For the sedans the electronic limit is set at the factory and is increases based upon certain specs. Performance tires increase the C43 top speed. Additionally, the C63s models have a higher top speed limit than the std C63. Again, this can be removed with an ECU flash from any reputable tuner.

An SUV is probably the worst choice for a track car. Just sayin.
My GLC is fast and handles well on the curves but a lot of smaller lighter cars would destroy it on any track that actually had a few challenging corners. HP does not trump physics.