Welcome to the Guild! This is an excellent map, even so if this is your first one.
The size of the mountains in not a problem.
Most maps require some abstraction : some element are depicted larger than what they should be so we can see them at the scale chosen to make the map.
It's also a matter of artistic preference.
Larger mountains may give the impression the continent is smaller than what it really is.
But smaller mountains sometimes mean a larger map, more mountains and more work to do.
It does look larger than Wales in my opinion. Well unless mountains are on scale.