I may be over thinking this. I have a 4k monitor. 3840x2160. Which settings do most of you run? Is there any preference or benefit?
** I did search threads and found a couple of posts but nothing for certain. My gut says stay native resolution and downscale for FPS.
Monitor/Game Resolution = 3860x2160
Render Scaling = 85%
Or
Monitor/Game Resolution = 2560x1440
Render Scaling = 150%
I would say for the most part you want to use the monitors native resolution AND refresh rate for best performance. Having said that, you want to ensure that your gpu is sufficient enough to run at these levels. For example, a Nvidia 3050 gpu is not going to be able to drive a monitor at 4k (1080p would be more like it).
So just to add to what I’ve said above, you really also need to bring your CPU/memory into consideration. An AMD 3500x paired with a Nvidia 4080 is probably not going to run 4k very well even though you have a high end gpu as the CPU is going to hold you back.
At the end of the day with MSFS 2020, it’s really about finding a balance between your monitor, gpu and cpu. Render scaling is one means to achieve this in certain circumstances. Easy peazy right? 
I run 4K, TAA, full Ultra with DX12, Scaling at 100, 69 Hz.
Whatever your equipment can handle.
My card specifies that it can only handle FSR2 at 1440p, so that’s what I use on a 4K screen. That was mostly limited by GPU.
For more fps there’s always DLSS quality or balanced, what you see depends a lot on your system and how you fly but of course there are drawbacks, slight to medium blurring and as with all gpu load easing settings LODs may need to be lowered.
Since discovering FG I now use DLSS+DLAA which is a little more detailed than TAA but with similar framerates and LOD requirements. I have nothing to compare with but my low latency ram (53ns) keeps everything smooth.
When I was in a similar situation with a 6600XT on a 4k monitor, I ran it at 1440p and 100% render scaling. I found that had less image degradation than leaving at 4k and render scaling at whatever was needed to achieve acceptable frame rates. I couldn’t use FSR at 4k because it increases VRAM being the 8 GB the card had. I’m now on a 7800XT. I can now run 4k and 100% render scaling, but I tested FSR compared to 1440p like I use to do. I still think running that lower native resolution with 100% scaling looks better than FSR on quality.
But it costs nothing but a bit of time to test and compare results yourself. You may find what works best for me doesn’t work best for you.
Is that definitely correct? I had always been led to believe that TAA was better for visuals, but I am open to learning and trying different settings. I think I did try DLSS a while ago and didn’t find it as good as TAA, but things might well have moved on.
I’ll give it a try and report back. PC is 13900KS, 4090 & 4K QD-OLED, so any difference should be noticeable.
I tried a few different flights in different areas from rural to very urban and switched between TAA & DLSS+DLAA. Using external view, DLSS did look pretty good but there was some shimmering in patches over water and a very slight softening of the overall view (I’d say too mild to be called blurring), which was actually beneficial on some sharp edges.
Switching to cockpit view though and DLSS is noticeably much poorer on my PC. The softening of the image was more pronounced with the small details and textures, and scrolling numbers on the displays or gauges were so blurred it was quite distracting. I tried various sharpening, scaling and ‘quality’ settings, but nothing reduced the problems enough to make it a worthwhile switch for me.
Using DLSS as opposed to TAA did slightly increase GPU usage and also increased FPS, but only by a very small amount. I generally get 80-90 in busy areas and complex aircraft using TAA which is more than enough so I’ll stick with that for now, but the DLSS option definitely looks better than the last time I tried it a couple of years ago.