Overlay question

[FreemanQC]

Hi, I'm trying to figure out the best way to have overlays for all my systems. I would like to know if these points makes sense.

1- Consoles: Shouldn't use integer scale as it puts the original system resolution which is often not 4:3. For example the NES, SG-1000, etc. So in Retroarch menu I would put the video output to 4:3 to get what we're used to see back then on our 4:3 CRT televisions. This also makes the process simpler, as I only have to build one 4:3 generic overlay for all my systems.

2- Consoles: Use Retro shaders set and not include the shader in my overlay as the Recalbox team already selected the best shader according to each system. Technically the shader should be perfectly aligned on 4:3 resolution.

3- Hanhelds: Here I would have to use CUSTOM in Retroarch because all overlays I tried doesn't work in pixel perfect. I have to manually resize X, Y until it matches the viewport. For that reason it would be better to keep the shader inside the overlay. Because obviously the Retro shaders set of Recalbox wouldn't be aligned properly.

This brings me this question: how can I use the Retro shaders only on the consoles/arcade?

If I can't do that, does the shaders can be included in a system cfg file just like the overlays?

Thanks a lot, hope this reads clear.