I followed a similar path... from 27" iMac to Silicon Mac with a 5K2K 40" Ultrawide from Dell. The built-in hub does in fact allow multiple computer inputs (4 if I like) and I can display multiple running computers in various ways on the same screen at the same time. One keyboard & mouse in the hub can control more than 1 computer. Once you go ultra-wide, there is no going back to the nearly square-shaped screens of Apple monitors. The extra screen R.E. is just too useful. Hopefully, Apple opts to roll out an iMac UW someday for those who are only able to consider technology with an Apple logo on it.
I'm also coming from Adobe Creative Suite history and have embraced Pixelmator Pro on Silicon. The latter is incredibly great as a substitute for Photoshop but is certainly DIFFERENT from it. If you have any intentions to do work with it at home and then bounce into an office/client office to then do more in Photoshop, it is two very different apps. If your use is solely for you and you simply want to be able to do about anything someone can do in Photoshop, Pro is quite capable.
Photo editing from a novice level is probably not demanding enough to warrant PRO. But key to your consideration is not what you are doing now but what you are wanting to do YEARS from now. This jump for you is 2023-2009 = 14 years. If you keep this next Mac for similar time- if Apple will even support Silicon Macs for that long- your computing needs could be quite evolved/different in 2036. Yes, you could have replaced this Mac sooner than that... but yes you could have replaced that iMac sooner than 2023. The point: just in case this is your Mac for the next 14 years, you need to take your best shot at imagining what you might want to be doing with it way out there.
Does photo editing eventually lead to video editing? That could start making a case for PRO vs. NON-PRO. Do you anticipate the photo-editing to become a very big thing, processing huge numbers of very high resolution photos like a Photoshop guru? That could start making the same case.
Your iMac had the very great advantage of FLEXIBILITY to evolve as your needs of it evolved. Silicon has no such internal flexibility. If you get to a point where it's simply not enough computer or RAM or internal SSD, you have to replace the whole computer. Thus, you need to choose the Mac you'll need maybe 7 years from now vs. the one you need today... OR assume that you may outgrow this purchase much more quickly than that iMac and be buying ANOTHER one in about that much time.