I recently purchased my first Fixie and wanted to build it up to have a few different setups. I wanted two wheel sets and one with set with an internal gear shifter in the hub with a more aggressive tire, and than a second set that is classic fixie.

Question one, for my special set should I do a hub swap or do it myself? Also can I put any sprocket on any rear wheel? Very new to this kind of project, any help is appreciated..