Images won't stay on top

That's called focus.  The active tab trumps all others.

Try Window > Arrange > 2-Up Horizontal or Vertical.  See screenshot.

Hope that helps.

Got the answer; it's designed that way to adhere to the Mac OS interactions. We often find ourselves stuck between following requests to break OS convention vs. adhering to those same conventions for consistency. In cases where there are entrenched and/or clearly articulated differences by design, we generally favor keeping behavior consistent on the platform vs. across platforms.

The specifics are that on Ps on Win, if you undock one document window, it will be 'in front' of the application container window all the time. With Ps on Mac, if you undock one document window, it will be 'in front' of the application container until you activate a document inside the application container. You can activate a document by clicking in the document area or by using the Window menu. When a document in the application container becomes active, then the application container moves in front of any floating document window.

I have seen some creative workarounds to this, though (pasting into Notes and using the Notes feature to always keep on top). You can also tile the windows in Photoshop and as long as an activated document doesn't use the same space as the source document, you can still have both on the screen at the same time (just sharing instead of overlapping).

Many thanks @Mark.Dahm.

It would be great to seamlessly go between osx/pc for workflow as a traveling freelance photographer. 

Let me do some slinking around the hallways for a few days. I'm guessing we've looked into this already, given the lonstanding nature of the request, but I'll let you know what I find out.

Thanks for the quick response. So until the Photoshop sees a fundamental framework change, we shouldn't expect this to be fixed in the near future in the current frame work?

I think I can workaround with the stacking/fitting windows feature in the "views" tab, but obv not ideal. 

The frameworks on Mac and Windows are different; we have a ton 'baked into' the way the windowing systems work on each platform, and are looking into modernization efforts to change those limitations so that we could tackle this. So while it is a recognized pain point, it's also a tremendous technical lift that will take a long time to ensure we don't break in some fundamental way.

I absolutely love the similar workflow power I have with the mac. It actually performs similar to my 13th gen i9 PC.

However the software/OS limitation is annoying the crap out of me. Windows 11 workflow with PS is far superior due to the tab/windows management. Any input on this @Mark.Dahm ?

I guess just live with it I guess since they haven't addressed a long standing issue for over a decade? 

I begrudgingly switched from Mac to Windows in 2020, while waiting for Apple to update their pro machines to Apple Silicon. Ps works on Windows of course, but little things like how the Wacom tablets respond, inconsistent color management, and the OS in general were constant annoyances. You deal with it. I'm getting back to work now on a new Mac Studio M2. And as much as I like it... there are annoyances. Here's one:

With PS on Windows, you don't really have a choice but to have the Application frame on. You don't get windows floating over the desktop. I prefer this. It's clean, and it keeps me focused. If you do float a window IT ALWAYS APPEARS ON TOP OF THE APPLICATION FRAME. This feature has become indispensable for me. I do a lot of color matching. Having a small independently floating window or two showing a section of an image that I can move around a larger, tabbed image that I am working on has become my standard workflow. I can open 20 files in a tab group, float my reference color images over the top of them and get to work, one image at a time. Honestly, I've forgotten how I did this before. Whatever it was was far less efficient.

On Mac, with the application framed any floating windows are sent BEHIND THE FRAMED APPLICATION when any of the framed tabs are made active. Why? Why can't I keep a reference image or two floating above the image I'm working on? If one attempts the workflow I describe above... it's impossible. Windows must be constantly resized. You cannot place a reference anywhere over the image you are working on and make adjustments while looking at the reference, as the reference get's sent to the back. As much as I hate to say it, the way this works on Windows makes so much more sense, and allows for a much more streamlined workflow.

I see this has been a request since at least 2014. That’s almost a decade.

https://community.adobe.com/t5/photoshop-ecosystem-discussions/how-do-i-keep-a-floating-window-on-top-of-a-tabbed-document-so-that-it-can-be-used-as-a-reference/td-p/6141600