With receiver and surround setup it all depends on the room and listening environment. Mcacc sounds like a version of audyssey etc. which should adjust your receiver to your correct room parameters.

You should be able to fine tune as needed and yes do go ahead and disable any extra sound functions in the receiver. Your sub performance will also depend on if you are sending it just lfe if you have full range main speakers or are using a crossover point which sends it some of the speaker low end bass content as well. You’re on the right track and will have to test some audio and self adjust and tweak from there. The sub should never overwhelm and sadly most people simply crank it up for the booming effect.

Center adjustments should be in receiver options on a single dB level. You’ll have to have a track playing and play it by ear with adjusting until it’s at a sensible level.

I would also suggest to toe in your main l and r channels toward your listening position.

In terms of best surround moments it will be more limited with the OT mixes due to their vintage. Overall you get so much more of the correct ambiance back in a HT setup that its hard to pick just one moment. You’d notice surround much more on the 97SE mixes which are great for their time. Easiest would be the prequel audio to get a sense of fully utilizing your setup. TPM’s theatrical Dolby EX audio is a must in the main sequences and will phantom center the rear surround behind your head if your surrounds are correctly placed.
I love the AOTC mix which is the best part of the film. For surround the no. 1 choice would be the Geonosis asteroid field with Jango’s seismic charges.