If you need to upgrade in the coming weeks, get the Intel-based iMac, especially if this is your first Mac and you're coming from Windows. Here are my thoughts as to why:
1) Apple's first custom-made chipset has really impressive performance, but the Intel-based systems are not slouches.
2) Nobody knows how long Apple will continue support for the Intel-based systems. When Apple first moved to Intel from the PowerPC-based systems, they continued support for the PowerPC systems three years after completing their transition and all systems were based on Intel. As of now, the iMac and Mac Pro lines are still on Intel. Rumors are that the iMacs will possibly shift to Apple's own chipset some time this year. The Mac Pro was last updated in December 2019 and there are no rumors as to when it will be updated, but it's not out of the realm of reality that it could also be updated this year. Assuming Apple follows the same time frame as it did with the PowerPC to Intel transition, Intel systems today are likely going to be supported for another 3-6 years, if not longer (because now there are more Intel Mac users than there were PowerPC Mac users).
2a) Even if Apple's support for Intel systems is shorter than anticipated, your computer won't stop working just because it's not on the absolute latest operating system.
3) You're coming from Windows. If you run an Intel-based Mac, you can ease yourself into the transition by purchasing Parallels or VMWare Fusion and running Windows as if it were an app. This lets you use all of your old Windows programs and usual routines, dipping into the Mac side when time allows. This was my conversion method: my first week with my Mac I was probably in Windows 95% of the time; by the second week it was more like 50% of the time, and so on. It's a less stressful experience and allows you to still get the most out of your computer, instead of juggling the Mac and a separate Windows system. There is a preview of Parallels on the ARM-based Macs, but it can only run the ARM version of Windows. The ARM version of Windows does have a x86 emulator, but... those are a lot of hoops to jump through if you're needing something mission-critical, and a lot of opportunities for something to not work properly. Not an issue with the Intel systems.
4) Intel systems allow you to use external GPUs, while ARM-based Macs do not - at least, not currently. Unknown if it's a feature that can be added in the future. Depending on what you're doing with Photoshop, exactly, this may mean more to you in terms of system longevity and performance than the Intel vs. ARM processor.
5) RAM isn't exactly more "efficient" on a Mac - macOS added memory compression before Windows did, allowing you to get more out of less RAM and sparing the swap file. It's still not a substitute for more RAM. It remains to be seen what Apple is going to charge and how high they'll build their higher-end systems' RAM, but there is something to be said for not only upgrading things yourself, but also choosing the timing and possibly growing with a system. And since you haven't told us what you do with Photoshop, nobody can really say if the current RAM offerings are enough. If you're working with multi-hundred megapixel images and/or tons of layers with crazy edits, you'll need more.
This is an uncomfortable time to buy an Intel-based Mac, but it's also an uncomfortable time to buy Apple's first foray into ARM-based Macs. The discomfort with buying an Intel-based Mac will increase with each day, but the worst time to buy an Intel-based Mac won't occur until right around the time that the last Mac system is switched over to Apple Silicon - probably in a year or two, although nobody can say for certain.
