wet the post with gallium and put a piece of duct tape over it, i'll fall over in an hour. no tools

"Oscillating cutters" are good for close cuts in tight spaces.

There's a tool that attaches to your drill or impact driver. Kinda expensive, but when you NEED it, it's worth every penny.

Oh, I should clarify, "the trades" isn't exclusively plumbing. I can sweat pipes and lay out a house but I'm no expert

That being said I always used a little stubby cutter for pipes close to walls

There's other designs, including ratcheting ones that look so much easier than what I used

Oscillating saw with a semicircle blade and a piece of paneling behind the pipe in case you get squirrelly with it