The simple answer is "try it." With a low value in the circuit, you can tack larger ones in parallel to experiment. Hard to parallel a 22uf down to anything... Up is easy.
In general, I think at least a factor of 2 if you want to hear anything. Off the top of my head, I am not so sure you will get any more bottom from your guitar above 22uf. From 22uf I'd try 4.7, sure or even 1uf. Plenty of amps out there with a .68uf bypass on a stage.
Same thing with plate load resistors, 100k to 120k won;t make much difference. The step up to 220k from 100k is a natural change to try. Of course any change needs to be considered in the context of the whole circuit.