With windows a large widesceen monitor will usually do the job of 2 monitors. Sounds like you don't need too much power. Unless you're into heavy gaming everything runs lightning fast - if you don't have junk programs or bad installs chewing on the processor.
Get something with a good graphics driver and spend more time looking at your monitor choice. On the PC, see that the USB + monitor I/O and accessibility fits your plug in work style. If you use Word and xl and Outlook you'll probably want to stay with a PC.
here is a decent dell refurb at newegg w/ win10 pro -
I didn't look to see if it has displayport connectivity - it certainly should.
Buy Refurbished: DELL Desktop OptiPlex 7040 SFF Intel Core i7 6th Gen 6700 (3.40GHz) 16GB DDR4 RAM 1TB SSD DVD Intel HD Graphics 530 Windows 10 Pro Grade A with fast shipping and top-rated customer service. Once you know, you Newegg!
I think that the one big vs. two smaller monitor debate isn't specific to Windows.
Macs have, by default, operated in "extended desktop mode" since the hardware was capable of supporting multiple monitors(right around 1986 with the Macintosh II and System 4 or so). In effect as many monitors as you can string together(and yes you can do 6 with a Mac II-I managed to piece it together at one point for a proof of concept) will just function as one single large desktop however you arrange them.
The original implementations of virtual desktops even use to change all the desktops together. Now you can set it so that they either toggle together or can be changed independently-I hated the independent change when it was first implemented but now use it and it's easy enough to change both when I want to.
I use dual 2560x1440 monitors at home, or rather one is a 5K monitor scaled to 2560x1440, while the other is that resolution native. Each 2560x1440 is wide enough to display two windows side-by-side at 1280 pixels wide each, or in other words about the width of a typical 13" laptop screen of a few years ago(most are more like 1440 wide now).
With that said, I've always liked two monitors for what I'd call a psychological advantage. As an example, I might be working on a document and referencing a web page or other material on one screen(my main task at hand) while I have background things going on like email so that I can rapidly screen and switch if something requires immediate attention, or perhaps another browser window to look something up occasionally and
Apple Music for background sound. My point being, though, that the main thing I'm working on/need to get done is physically separated from background tasks, and that's a valuable tool for me. Others may work differently, but as long as I have the space I don't see not having two monitors.
At least in serious photo editing too, and I'm sure other graphical tasks, many people will spend big bucks on one high end, purpose made color accurate monitor(not necessarily a $10K reference monitor, but maybe a really darn good $3K one) for critical viewing and use a second less expensive screen for bulk sorting/culling/etc or even in programs like Photoshop pushing all of their tools/palettes off to the side to get the most working space possible on their good screen. Back 20 years ago when even really good LCDs had terrible color accuracy, a lot of guys would put a big CRT on their desk-often something based around a 21" or 24" flat Trinitron tube-and then have an LCD for all the other stuff.