Regarding pros and cons of Global vs Vol Block pedal control...
One important consideration is reverb and delay trails. Any vol control that appears at the END of the signal chain will either increase or attenuate the trails, along w/ the signal. For many people, myself included, that's a non-starter.
So, then, you start premeditating whether you want your vol control BEFORE the amp (which then affects gain, distortion amount, etc) or AFTER the amp (which keeps basic tone consistent). There are a bunch of options for doing either of those 2 approaches... but they all wind up being done on a "per-preset" basis.