Hi Rob!
I was in a similar situation but my main production machine was a 2014 5K SSD only iMac that has been experiencing some unpredictable crashing episodes.
I ordered 3 M1 Macs to test and sent the first 2 back.
Test 1 - base Mac mini - returned - I had problems with my existing Apple Keyboard and Magic mouse connecting reliably. While troubleshooting with an Apple Support rep on the phone they had me try to reinstall the OS and it bricked.
Test 2 - base Mac Book Air & LG Ultrafine 4K - returned - When importing and generating previews the Air was painfully slow, taking 2-3 times longer than my 6 year old iMac, I believe due to cooling issues. The 4K seems like an amazing buy for $800 with the TB3 in and out, supplying power to the Air, and acting as a dock, but going from the 218PPI of the 5K to the 183PPI of the 4K was completely unbearable for me. A7r IV photos that were in focus and look great on the 5K looked soft and bad on the 4K. This is the same 4K screen that will come in the iMacs Apple will announce Tuesday. For anyone coming from a 72PPI or 102PPI panel the 4K will probably be excellent, it unfortunately not for me.
Test 3 - maxed out Mac mini, Apple Magic Keyboard & Magic Mouse 2, LG Ultrafine 5K, & OWC 32TB Thunderbay 4 - still testing - I'm having issues importing from folders that contain jpgs so until that is resolved I can't fully test or recommend this setup. I am in touch with Apple, Adobe, and OWC support and hoping to have it resolved soon. However the 5K is terrific, night and day better for me than the 4K, I just wish it had a TB out like the 4K. The OWC Thunderbay 4 is seeing speeds in the mid 700Mb/s, and the internal 2TB SSD is seeing speeds in the mid 3,000Mb/s, yes mid three thousands! I whole heartedly recommend the largest internal SSD you an afford.
In addition to the insane improvement in R/W speeds you'll see with an M1 LrC is equally impressive even still running on Rosetta. Flipping through previews is instantaneous as is transitioning modules. On my 2014 iMac it could take 3-4 seconds for a change made in the develop module to show, but everything is absolutely instant on the M1 now. The RAM on M1 is a totally different concept than RAM as recommended by Adobe. LrC never maxed out 8GB when I had it even when importing or editing 1,000 ARW files from my A7r IV. Now that I have 16GB there is plenty or headroom, I can even run Chrome lol.
Bottom line, the M1 chip is great for LrC and will be a massive improvement over your 2010 iMac even if you only get 8GB of RAM. Get as much internal storage as you can afford and don't skimp on a display. Without the Thunderbay and 5K, but using the 4K ($700), Mac mini ($1700), & Peripherals ($250) that's only $2,650. Using the base Mac mini thats $1,650. It's likely that the base 24" 4K iMac announced Tuesday will be at least a couple hundred cheaper. I don't think I'll ever go iMac again just because I want to upgrade the computer more often than the display but it is the most cost effective way to go for most people. What ever you do, I'm sure you'll be very happy with the M1 and LrC performance on Rosetta. LrC on M1 will hopefully even improve quite a bit more.
Tim