I used to have a 2019 27 inch iMac and I upgraded to a new Mac Studio. I got a base model and upgraded the hard to drive to 1 TB and the ram to 64 gb. I also got a 32 inch LG 4k Monitor.
I got a 4k 32 inch monitor since this was around 400 and the Apple 27 inch 5k monitor was 1600. The LG monitor is bigger and is 80 percent of the Apple monitor for a lot less. I would really like the 32 inch 6k Apple display, but it is 6000.
I got a new computer because I typically upgrade every few years. The Mac Studio has a 10 core M1 processor. The read speed of my hard drive is about twice as fast as my iMac.
I also upgraded the ram since Lightroom uses a ton of ram. Activity monitor on my mac typically shows I use around 50 gbs of ram (this is everything and not just LR).
In day to day things my Mac Studio is not faster than my iMac. However when I run LR it is faster than my iMac. Also the computer is really quiet. Since the hard drive read and write speed is faster the restart time for the computer is really fast. Another aspect I like about the Mac Studio is the abundance of ports. The mac mini is a great computer, but is lacking in ports.
Overall the Mac Studio is great and I have been very happy with it. Yes I paid a lot for it, but I use it every day since I need a fast computer to run my photography programs.