School me on adjustable gas blocks

[peak98]

None of my uppers (6.5gr and 223) have adjustable gas blocks but they’re 16”-20” barrels. I recently picked up a 12.5” upper from the classified. It has a standard gas block as well, I am waiting on a BCG to arrive to try it out. Lower is an AP with sb3 arm brace. I do have an AP adjustable block that I picked up with the intention of using on a pistol build. I was told by my gunsmith that an adjustable block isn’t necessary unless shooting suppressed (not at this time). What are the pros/cons for a Grendel pistol with and without the adjustable block? Would I be better off running a h2 buffer? Please let me know your opinion and the reasoning behind it. I’m wanting to learn and understand. Thanks.
peak98