Video smoothing often makes the picture way too mushy for my taste, especially if the original resolution is very low. I prefer good crt shaders like the zfast shaders from @ghogan42.
As for other video settings, I prefer the "core provided" aspect ratio, because I don't like, say, a 4:3 picture stretched to today's common 16:9, or the 3:4 ratio of many classic vertical games stretched to the native 4:3 on my DIY cabinet, making all game characters appear a little overweight to outright obese.
@agtrigormortis Yeah, I have that problem with several games I'd like to have. The 1992 X-Men beat 'em up is a prime example. Apparently I missed the boat for it being on XBox and Google Play. It's too bad companies don't do more collections and ports for those who can't afford to be arcade collector enthusiasts and don't want to be pirates. But on the bright side there are a lot of options for many of the best arcade games in the collections that do exist.
[just whispering and OT] @clyde And the Sega Megadrive & Genesis Classics where already mentioned/discussed in that thread more then once :P maybe it would be time to split that one into "collection of sources" and "announcements for sales" for items from "sources" %^]
Nobody here (of consequence) will hold your inexperience against you. It's just that most beginners' answers are already covered in the very comprehensive documentation of this site. In your case, the link that @dankcushions gave you leads to a page with a section called "Boot to EmulationStation“ which for its part links to the FAQ with exactly the instructions you ultimately needed.
A typical approach of many veterans not only in this community is to help others at helping themselves by pointing them in the right direction, but at the same time expecting them to do the (usually manageble) learning by themselves.
Just trying to calm the waves a little. Welcome to this forum, and have fun with RetroPie. 😁
(@dankcushions beat me about his link while I was typing this.)