OP, how much experience to you have with live sound engineering? What types of venues do you play? Tell us about your band and the type of music you play.
Right. I have very little experience with live sound engineering, but I did do some studio work as an engineer years ago. The equipment has changed a lot, but the fundamentals are still the same. I'd say I'm an advanced novice, lol. I find it very interesting and I want to get better at it.
Our band plays rock and Latin rock covers, mostly from the 80's and 90's. We play mostly pub-style places that serve lunch and dinner with live bands and DJ's in the evening. Not very large rooms, but a lot bigger than your average dive bar. We run my XR18 into a Behringer NU3000DSP power amp and into two sub/main stacks. I don't know the specs of the speakers, but they are Behringers. I think the subs are 18's and 12's with horns on top. It's plenty loud and deep, in my opinion.
Drums, bass, one guitar, keys, and a female vocalist. The drummer and guitarist sing backups and each of them sing lead on a few tunes. Our vocalist employs a harmonizer on some tunes, she controls it on-stage. Most of our songs are guitar-based, and one of the itchy points is the fact that the keyboardist is not great at complimenting songs that don't have a pre-baked keyboard part. So I have to balance making him heard so he is happy, while not turning him up enough for his clanging to annoy everyone.
We are all using IEMs since I got the XR18, and everyone has their own aux mix to control as they see fit. So I don't have to worry about monitors.
Running sound is often a thankless and stressful job....even when sound is your sole responsibility. However, I am pretty picky about sound and usually find it even more stressful when another band member does the job.
Oh yes, I am with you. The keyboardist was doing it before me, and I never saw him move a slider. He used the gain knobs to adjust the mix. Half the channels were clipping. I just can't.
I have done that a few times and key is to tell your band mates to not increase their volume ones the show starts.
Since the drummer WILL get louder once warmed up the band will get louder. Account for that.
If anybody complaints, tell them to STFU.

well, maybe use some nicer words.
I'm still getting adjusted, but once I get everyone to say "hey this sounds pretty good!" then I'm going to tell them that if they want me to continue to run the sound, then I am the sound man. I'm open to constructive criticism, but I'm not making ice cream sundaes were everyone gets exactly what they want. They have to trust me and get out of the way. Once of the reasons I got the XR18 is because there are no physical controls. The band members can no longer just walk up to the board during the show and adjust things. Yes, they were doing that. I am the captain now.