Since the 27" Intel iMac seems to be dead in the water now, no M1 version of it apparently going to be appearing on the horizon any time soon, it seems reasonable now over the next few months to be looking at:
An M1 MacBook Pro either on its own or with an attached larger external display and the machine set up on a stand either remaining open or put in clamshell mode, plus peripherals
An M1 Mac Mini when it is next updated, and since it is headless it will need an external display if you don't already have one, plus peripherals
A Mac Studio (either Max or Ultra, take your pick) plus external display and peripherals (mouse, keyboard and if you prefer a trackpad, one of those)
At the moment I am using a 15" 2018 MBP with a 24" LG 4k Thunderbolt 3 display and the appropriate peripherals (BT Apple Magic Mouse II and Magic Keyboard). My last iMac was a 2012 one and I had been looking forward to when Apple would been releasing the first 21.5" one with a retina screen. When that finally happened, I read the specs, was disappointed and started considering my options. A 27" iMac was not among those options. Too heavy for me to handle physically, too large a display screen.
I started considering the advantages of an MBP and the flexibility which would come along with that, so I experimented a bit at home with putting the 13" MBP that I had at that time on a stand and using external peripherals with it. Decided that this approach definitely had possibilities and I particularly liked the idea that I could walk into my local Apple store and buy a 15" 2015 MBP right off the shelf that was specced pretty much exactly as I wanted. That worked out so well for me that in late 2018 I did the same thing, simply bought a 15" 2018 MBP at the store, brought it home, set it up on the same stand with the same peripherals and was more than happy. The three years in between gave me ample time to begin transitioning with cables and such for my external drives so that when I had the 2018 machine on the desk I was able to easily transfer data by swapping cables on the external drives as needed.
During those years, though, I wasn't doing much with photography so that the 15" MBP screen was perfectly fine for me, but once I got back into more frequent shooting again and subsequently editing many images, it quickly became apparent to me that I needed to get an external display, which I did -- the one mentioned above -- and that has worked out very well for me. Yes, I know that for a lot of folks a 24" display is considered to be too small, but I had found a long time ago back in the days when I had a 30" ACD that it was too large for me and that I kept having to swing my head from side to side to view everything on the screen, which is unacceptable. The large screen real estate was great for pixel-peeping while working on images but not so great when simply trying to read emails or forum posts. I had also earlier found that for me, 24" is the "sweet spot" for both editing images and reading text on forums and in email. Aside from that, since I live alone and I'm the one who has to wrestle any new item out of the box and on to the computer workstation, then set it up, it's best to have something which I can actually physically manage at the time of purchase plus at any time that the equipment needs to be moved around for whatever reason. No problem with an MBP or Mac Mini, of course, but external displays can be surprisingly heavy.
in the meantime, you might want to update from Big Sur to Monterey; that might resolve some of your issues with your current machine.
Everyone's needs, priorities and experiences are different, of course.....