You are all correct if it works for you :)

I like using two identical miniPC's, one for each monitor.

Well, actually each monitor has two inputs and each PC two display outputs, and I had a couple extra cables so they are cross-connected too but that's besides the point.

Seems like RDP is almost intended to work like this from the beginning. Deficiencies are a lot easier to tweak side-by-side too.

Decades ago I just had to accept that a key purpose of introducing multi-partitioning to HDD's was so that multibooting from a single HDD would be extremely straightforward. And once set up, very closely mimics the hardware behavior of having a dedicated HDD or SSD for each of Windows and Linux, on the same PC.

Previously, with two different HDD's connected, each completely unaware of the other one upon power-up, when you reboot you can always use the motherboard's built-in BIOS boot menu to choose when you want to boot to a drive other than the one designated as the default choice.

That way there is nothing related to Windows on the Linux HDD at all, and nothing having to do with Linux on the Windows HDD. You can physically remove either drive before powering up and everything works completely dedicated to a single OS as expected, because each HDD is complete including its own boot files, exactly the same as it is in a non-multibooting arrangement.

As long as each HDD is capable of booting on its own, you choose the one you want, and that's the one that boots.

Well it actually took a while in the '90's before most motherboards had a built-in BIOS bootmenu to choose between different HDD's, but this feature became universal so users wouldn't have to physically reconnect their intended boot drive to the Primary Master cable. Which was the only bootable connection before the BIOS bootmenu made Secondary-connected HDD's as bootable as Primaries, your choice. You don't really have to get the most out of the electronics, but some things like this are really nice to have.

Now this was the time when it got real fancy, and both Windows and Linux bootloaders were crafted to accommodate "chainloading" from a Primary HDD to a non-Primary, so physical reconnection would not be necessary to accomplish the same behavior. This was ideal for all the remaining motherboards at the time which were not issued with a BIOS bootmenu. This is where you start to get a mixture of Windows and Linux on the same HDD, at least in the boot files. It doesn't have to be confusing, but it can be.

Once one set of boot files can boot either OS from any HDD, then each HDD no longer needs its own boot files, however that also means that those HDDs not having boot files would not boot if they are the only HDD connected.

I say the BIOS bootmenu is the fundamental that is best not abstracted too far.

Fortunately, multibooting to various SSD's using one single (Linux) bootloader [0] can be configured to have the same hardware workflow as choosing separate HDD's through the motherboard bootmenu.

And to be the most consistent I like to use the same workflow to choose from multiple partitions whether they are on the same HDD or not.

Now you can figure it's all moot, with separate miniPC's for Windows and Linux. Which really could be considered more of a luxury than multibooting a single-drive PC at will, and even more versatile than having two SSD's in the same PC.

But wait a minute, each one of these drives on each PC is a massive multibooter . . .

[0] The Windows bootloader works as always on MBR-layout SSD's on PC's supporting traditional BIOS mode, but still too defective under UEFI, where Microsoft drops the ball completely since Windows 8 in the key area of multibooting Linux. Which for decades was as easy as intended by the hardware design. But negative progress is accepted as progress by those who are supposed to be experts, as we have been convinced.