Speaking of Amiga & C64 emulation, I would use FS-UAE for Amiga and the VICE core in retroarch for C64. FS-UAE is much simpler to configure than WinUAE, I heard, but with the same excellent results, including a decent built-in scraper for your box art and screenshots.
Yeah, Rusty claims FS-UAE is easier, and probably he's right. However, WinUAE is not hard to set up either, it's a bit overmystified, really. I made comment about the WinUAE setup a few months back, you can look it up. One area where FS-UAE is superior that I know of is that you can enable aspect ratio correction by enabling a single option -- it's much more involved with WinUAE (again, I made a comment about that).
I'm curious to see how Amgia games look with the CRT-EasyMode (halation) shader which is easily set-up with FS-UAE, I understand.
Well, post some screenshots if you get some authentic-looking results. I know how the output of the C64 looked like hooked up to a TV set, and the Amiga to a typical colour RGB monitor from the 80s, but none of these fancy shaders do it for me, all I've tried to just looked like crap, in my opinion. So I prefer sharp pixels. Having said that, I like the PAL emulation in VICE a lot (the C64 was really meant to be used with a TV), I just dial back the blurriness a bit.