I used a Time Machine back up from a 2011 iMac to my M1 Studio. I cleaned up some old documents to an external hard drive first. That was a lot of years of crap.
I thought about transferring everything, but then I just set up the Mac Studio new. Added fast external storage. Build very organized file folder structure. Made sure all notifications etc are blocked. Set up all display and input preferences as I walked through my old mini. Went through every other setting in the menu to make sure I was using the new hotness and not using what I never liked. Then I individually brought over the software I am still using, which is not necessarily what I have accumulated over 6 years. Total squeaky clean start. Old mini stands alongside, every week or so I find that I need a file or something I forgot to bring over and turn on the mini to get it. Loving the "clean" new start as I had no discipline with the mini.
Disclaimer: mine is a Mac Mini 2018 to a base M2 studio.
I have been analyzing that there is a lot of software installed on the Mac mini m1, and I dont use all of it. I have so many configures apps and websites, that I would like to not loose any of them. Because of the time spent in initializing a new Mac, and the fun of doing it again from scratch, i am tempted to do it. Still very undecided.