Sluggish graphics with M2 Max and dual displays

It is possible to assign applications to specific Spaces/displays - provided that you have at least two Spaces on each display. To do that, you click and hold the application icon in the Dock and choose Options->Assign To->Desktop on Display x (where x is 1 or 2, when there are two displays, 1 being the main display).

Also: even if you don't assign specific Desktops to an application, you can "launch it in a certain display": click on the desired display (I typicall click on the menu bar on that display) to make it "active" (notice how the menu bar is highlighted and the one on the other display is dimmed); press command-space and type a few letters of the application (e.g. TextE for TextEdit, or Saf for Safari), and press enter. The application will start on the active display unless it is specifically set to run on another.

I have to say that I do not experience applications moving, i.e. if I quit an application and then start it (even in the way described above), previously existing windows reappear in the same display that they were before I quit the application.

It could very well be an issue when managing a single Space that goes across two displays.

I have never turned "Displays have separate Spaces" off in a decade or so, as the only possible benefit is to allow a window to extend over two displays; for my workflow that is never useful, but for example having a video running fullscreen on the second display is.

Alas, I don't have the time nor the same software you mention, so I won't be able to test this.

You may want to report this to Apple via the feedback page:

https://www.apple.com/feedback

Re: Moving windows. I have use two 3rd party apps to put my windows where I want them

Stay

https://cordlessdog.com/stay

Moom

https://manytricks.com/moom

I am currently using Moom, but there is nothing wrong with Stay, and in fact Stay is a bit easier to figure out.

When I wake up my Mac from sleep, my Windows on the 3 monitors I use are not where I want them. A 32" DELL 4K, an Acer 28" 4K, and my 14" MacBook Pro (M1 Pro chip). They are attached to a CalDigit TS3 Thunderbolt 3 dock. The DELL via the output Thunderbolt 3 port to the USB-C cable that came with the DELL. And the Acer via a DisplayPort cable which I provided. The dock plugs into my Mac via a Thunderbolt 3 USB-C cable that came with the CalDigit.

I just press the "Hot Key" I've assigned to Moom so that it will put all my windows where I want them.

NOTE: I am not seeing any performance issues using my 2 external 4K monitors. However, my usage is different from yours. Mostly I run iTerm2 terminal emulator (I live in a terminal emulator ssh'ed into remote Linux development systems), Safari & Brave browsers, Thunderbird for work email, and the Cisco Secure Client VPN (which I use to gain access to the company's network; otherwise I would not run a VPN). Preview is often open as I frequently take screenshots and annotate them via Preview. Carbon Copy Cloner, SuperDuper and Time Machine backup utilities run on various schedules (I am paranoid about backing up my data). I have Activity Monitor running all the time, and my work load is sufficiently light that my CPU cores are running just slightly above idle.

If I quit my apps, they come back to where they were when I quit them.

Where I get into trouble is that when I put my Mac to sleep, I unplug the CalDigit to remove power from the Mac (difficult for overnight thunderstorms to take out my Mac; have not lost a Mac, but I've lost printers, comm gear, an ethernet port on a Mac years ago, a well pump, etc...). Anyway, the Mac will wake up in the middle of the night, and find that 2 external monitors are missing, and it will cram everything into the 14" display. In the morning when I plug the dock into the Mac, the Mac moves some windows to external montiors, but not all of them and not at the correct sizes. So I use Moom.

Yes, what I do is not typical, but it is what I have evolved to satisfy the "Anal Retentive" bits of my personality 😁