Right now? Buy any more recent 27" iMac - models from 2019 or 2020(please see if there's even a 2020 model iMac - I believe there were, but I am not sure)
I think even a 2017 model would suit your style of a big monitor and a Mac.
If you can then I would in the same breath advice you to hold off until the larger monitor M1 iMac's come out. Which shouldn't be long according to rumors from China.
There's a thing here I'm a bit afraid of suggesting--- switching over to the Apple Silicon Macs coming from Windows. I think you might enjoy it and the CPU translation service; Rosetta 2, should handle all the Intel woes.
The top 27" tier iMac from just a few years back is no slouch and I think you would enjoy having an iMac with 1TB SSD or half that as well as 32GB ram and 8GB or more graphics card RAM.
How well the supposed 32" Apple Silicon iMac's will hold up is anyone's guess. Judging from the current 24" M1 iMac models I think you're good on selecting that one too.
Adobe's applications are slowly getting rolled out for M1 processors - I think Photoshop is in Beta right now.. someone could correct me on that. Be careful with Adobe and modern Macs. Since more modern macOS are 64bit only - your only choice is their Creative Cloud service. No older 32bit versions of Photoshop will work. This has been discussed many times and there's been a lot of cursing behind the screens I imagine.
For your viewing applications you could look into an oldie called XnViewMP - that is primarily a Windows application. Not that you asked for tips on applications, but that should get you going.
There's plenty of these viewing applications for the Mac. macOS has great built-in viewing services too. Preview and the famous QuickLook feature. XnViewMP gives you a good overview.
A more modern solution for the Mac is using Pixave.
FTP is carried out best using ForkLift, Transmit and CyberDuck.. beware that these last two programs mentioned has become somewhat of a money grabbing service. ForkLift is multi purpose and is really a file manager at heart, but it does so much more than that.
Again, I know you didn't ask for tips on applications.. I'm only helping you out so that you have a starting point at least. You can try asking for further assistance in the Mac Applications sub-forum here on MacRumors. There's probably lists too. Of course, should you be so bold to try MacPaw's service for applications called SetApp - then go right ahead. Again, this is a money-grabbing situation of sorts as it's mostly or yearly subscriptions that is the worst right now. Some Mac application developers kindly offer a free switch over license for a competing application or swap out a Windows license code for a given app in return for you getting the macOS equivalent license code.
If you try writing a macOS app developer in kind tone, then there's a chance they return with an equal kind tone - especially if for the purpose of achieving a license code for an application, let's say.
Or maybe I am too naive