The only difference I can see for text is the dropshadow is far more subtle with the filter on.
If mGBA doesn’t have similar shaders or filters to what you’d like, you can use Retroarch as a front end. It has terrific shader libraries available. Some shaders have also been ported for Reshade as well.
ShaderGlass is also an alternative for software Reshade cannot hook.
If you notice strange pixels that don’t seem to be uniformly scaled, it may be an option you can change. An example of what I mean:
