>>8927362
The Sampler stuff doesn't matter as much as you'd think, outside of working vs not working. Anything ending with _a stands for "ancestral" which basically means that the image will not converge on a "solution" but will continue changing with higher steps (not necessarily to the better). Non-ancestral samplers will converge on a "solution" image. Automatic vs beta is germane past works/glitches.

Lowering sampling steps will decrease your time but I've never had luck with my setup at values <18. There are models that work at very low step counts but I've never used them.

As stated above, CFG is roughly analogous to contrast. It's more than that, and higher CFGs give you more colorful images, but that's 99% of what it is.