A few things that I remember about those tracks, will list more observations once I can get back to the studio...
1. Groove was good overall but there were LOTs of rhythmic flubs that made it come and go - usually the acoustic hitting late or the bass groove - there was a single note in the bass groove that was critical to nail every time so when that one wasn't dead on, it hurt the groove - also that one slide up/down note would have been better if done every other time instead of every time. I didn't fix them but I did fix maybe two late acoustic hits that I couldn't live with.
2. Bass player overplayed in some places. Especially during the outro, I purposely did not try to make those chipmunk bass runs audible in that section because it was already occupied by the lead guitar part of the outro. I'm not one to constrain a bass player, but all that noodling during that section was a poor choice since two other guitars already had it covered.
3. I think several of us cut back on the guitars during the verses. I found it interesting that several of us did that on our own. I'm assuming they were left in for the mixer to pick what they wanted but had I been in that band, the first thing I probably would have addressed is that all musicians are all playing almost all the time.
4. Bass guitar recording, maybe I'm spoiled but those were far worse bass tones than I can typically get in my meager home studio in my sleep - by a large margin. My guess there was that it was a 'mic it then plug in and go' session rather than a let's get great tones then record session.
5. There were some motifs that could have been more aware of and out of the way of the vocal, don't remember which, would need to go back and review but it is a common oversight.
Re: Reaper plugins
I was a little disoriented at first but not long. I didn't find myself really needing non-reaper plugins except for saturation and limiting type stuff. What that means is that many of my third-party favorites are probably my favorites because they are plug and go, where to do the same in the reaper plugins I'd have to step back and consider individual params and know the numbers better. I also likely should have explored more JS plugins which I did not do.
If I had to mix all day everyday with Reaper plugins then I could see value in plugins that offer a faster workflow but the reaper plugs were plenty capable of doing most things and they were definitely not always slow, only for certain things.