I'm no expert when it comes to those technical software shenanigans, so what follows could be mostly inaccurate (to say the least).
But I'm fairly sure that very few games (if any) ever allowed the use of two different AA methods at once from their in-game options. To use two different AA methods normally you'd activate one from the Control Panel, and then if possible activate another (different) one from in-game options. I would assume that in most cases for games and in-game options developers aren't allowing it since, perhaps, it might cause issues or visual glitches... but that's just assumption more than knowledge on the subject. The only thing I can think of for games doing something like that (or allowing that to happen) is maybe some of them where it's possible to use FXAA while leaving something more typical / conventional like 4x or 8x MSAA activated (if both options are there and if both can be turned on at the same time). Most games I can think of that offer different AA methods in their options would grey-out one option if another is used, and vice versa (if you'd use FXAA, then it would grey out MSAA, etc). With this said though, I do remember seeing in-game options offering one option where it says something like "FXAA + TAA" or something along the lines, where basically it already combines two different effects together with the selection of one single "method" per se. I think that a recent update to the PC version of Monster Hunter World actually has one such "hybrid" AA option available (I own the game I could check it out, I just haven't touched it in months).
From the few guides I did read a couple of years ago on this subject the one main point I always kept in mind was that, overall, the "best" option is to simply go with one method and push that one method's sampling to the max of your hardware capacity while trying to keep performance in check. So if your GPU can push something like AA with a ludicrous amount of Supersampling on top of it then go for that. I also remember reading something about a "Shimmering" effect, and how some specific types of AA methods (or 'forces' or sampling) would be more harmful to image quality than anything else (but I think that one is on a game-per-game basis, or game engine-per-engine basis). However, what I do know is that with a third party tool like ReShade it's possible to 'force' its own method of AA onto the game (it has FXAA and MSAA I believe; maybe a third one but I'd have to check again), while the game itself applies its own version of whatever AA method it uses (from in-game options, or if not, from the official Control Panel). I think it's also possible to do something like that with NVIDIA Inspector, although that one I think mostly overwrites official Control Panel values rather than applying 'extra' effects like ReShade does with different shaders on top of the screen (like overlays).
Now with all this said, purely on a subjective level and speaking for myself... while playing, when things move, when there's motion, when my character moves, when I am in the middle of a firefight or when I'm trying to survive in a dungeon or try to beat my opponent in a fighting game or try to finish the lap first or... whatever is happening, there's one universal thing I always noticed: that I do not notice anything above 4X AA with jaggies. I've tried my fare share of AA methods and sampling powers and whatnot over the years I've been playing on PC and maybe save for a very few select games that I'm not thinking of right now I sincerely never noticed any big / major / notable differences with anything beyond "just" using a typical old-ass method and sampling amount like 4X MSAA. In the end (speaking for me here) I think that what actually improves image quality during game motion WAY more than just applying more AA would be actual Textures resolution, Render / Draw distance, sheer models / mesh Polygons count.
BUT... but...
Proper (or more) AA methods for images, for 3D renders; for anything that basically is 'still' and doesn't move... ah, then ok, at that point we're talking something different. It does make a good difference for that stuff. I myself am a (very amateur) 3D "artist" (I don't considering myself an artist but then again I don't consider myself a content creator anyway so I don't quite know what to call myself when I do that stuff so... yeah I'll just go with "artist", air quoting it feels better). For my renders, using Unity (can't use Blender yet, not good enough) I'm using ReShade. But instead of applying "more AA" to increase image quality I apply other, more 'exotic' effects that you would NEVER see from in-game options. Something like Denoise or Deband can make miracles to hide imperfections on textures when zooming in. It can also help fix AA-related visual / edge glitches. I don't quite have the vocabulary with the proper terms to explain the hows and the whys, but it sure as hell makes a big difference. I see it happen mostly when I do 2x, 3x or 4x close ups of my renders before "finalizing" them. But all of this only relates to 2D / 3D renders and maybe photography as well. But when it comes to real world photography I know absolutely nothing and I'll keep my mouth shut on that one.
Anyway, most of the above wall of text probably contains inaccuracies so take all of this from my own experience with a grain of salt. Maybe Google / YouTube would give you better information on this subject. There's millions of guides out there explaining basically everything possible there is to explain about all methods of AA out there, which ones are "best", which ones have been tried before and are all but forgotten today, which ones are old but still effective, which ones are being worked on today and so on, and so forth.
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