Ermm, yes you can Mix. You mentioned PAE yourself & I've used it with Linux - 8GB RAM on 32-bit. For many distros if you have the RAM and choose 32-bit a PAE enabled kernel is automatically used.
I wouldn't call it an artificial limit as such but you can't argue that MS deliberately chose not to use PAE.
Last edited by le Pingouin; 18th July 2013 at 15:57.