If you want scanlines you can use overlays, I usually set the RPI 1080p scanlines with a 0.15 opacity and they look very good. Or you can also test the scanline shader thats under misc, but it only works with integer scaling.for real CRT effects, there is a shader that mimics the SNES under a crt I think its called SNES composite, but I am not sure, and that one worked fine, but I personally don't like those effects.
I actually like those effects as long as they are not over-the-top. Some take it pretty far with trying to emulating a CRT's curvedness, color-bleeding and such. But in the end it's the scanlines that are most important to me so I will have a look at those overlays, so far I only knew about the shaders.