Mac support for non-native resolution

I would like to figure out which Dell monitors support non-native resolutions on Mac.

When I say "support non-native resolutions" I mean the behavior of the S2817Q. I used a friend's Dell monitor (S2817Q) that nominally had 4k maximum resolution (3840x2160) but also looked really good, with extremely sharp text, at a scaled 3k resolution (3008x1692). When set to 3008x1692, I used my mac's System Report to figure out what dimensions my Mac thought the monitor was, and it said "Resolution: 6016x3384; UI Looks like: 3008x1692." So, the monitor was behaving like a 6k monitor as far as my computer could tell, even though the monitor's specification says its max resolution is 3840 x 2160!!! That is the magical support for non-native resolutions that I am looking for. Similarly, when I selected 2560x1440 resolution, the System Report said "Resolution: 5120x2880; UI Looks like: 2560x1440." Furthermore, in the menu for System Preferences --> Displays, the resolution options appear as "Larger Text ... Default ... More space," with a little thumbnail for each option, just like the resolution options for my Macbook's built-in display.

In contrast, I purchased a new 4k Dell monitor (G3223Q) that doesn't seem to support non-native resolutions. The resolution options appeared as a list rather than thumbnails. I don't really care about the UI of the resolution options, but when they appear as thumbnails, I think it signals some special kind of interoperability between the monitor and my MacBook. The monitor's spec said its maximum dimensions are 3840x1692. The scaled options did not include my preferred 3008x1692 but did include 2560x1440. When set to 2560x1440, the System Report said "Resolution: 2560x1440; UI Looks like: 2560x1440." So no special magic happening there. 

I want to purchase a new monitor with behavior similar to S2817Q with respect to non-native resolutions. (I don't want a refurbished S2817Q because the stand is not adjustable in the ways that I am looking for.) I am currently shopping for Dell monitors, and looking at the details in the user manuals to try to find what I am looking for, but I don't know what specifications to look for. I just don't have the technical words to describe "support for non-native resolutions." Does the monitor hardware have more physical pixels than its specified maximum resolution of 3840x1692? Does the monitor software have special support for in-between resolutions?

Please help me out by telling me the technical language that describes the behavior of the S2817Q with respect to non-native resolutions, so I can shop for new monitors that have the same feature.