Does having more RAM than my Windows edition supports impact performance?

Solution 1:

No, it will not affect performance. It only maps the amount of RAM that the particular edition supports, that's all.

Solution 2:

On modern hardware it will not affect performance at all.

There are exceptions, such as in the Pentium 1 era where some chipsets could not cache memory above 64MB (yes, megabyte, not gigabyte). I think it is safe to assume that you are running server 2008 on more modern hardware though. :)