Assistance with new project

[Megamangel]

Hey! Glad to be around you guys. 
I’m trying to get this project but I’m not really sure about how to execute it.

I’d love a small system, I can see raspberry 4 is the most new with different RAM options (1, 2, 4, 8GB).
What I’m planning to do is to set it up with different things:
1.   I’d like to play several videogame emulators (up to 4 players)
2.   I used to have a small jukebox, I could play music videos and karaoke as well as music
3.   I have another drive 2TB USB 3.0 with tons of media I want to display.
4.     HDMI is a must since I want carry this everywhere I go

My problems are:
1.   First, there is no stock for the raspberry 4, is there any other hardware I could use?
2.   How much ram is stable for my project? I done want to require 2GB and have more if it’s not needed
3.   I've worked with Maximus Arcade on a PC I had. This works on windows, is there any close software for what I'm trying to do?

I like the raspberry since it’s size makes it completely handful to travel with.

Let me know your comments.
Thanks!

[tristan]

I run Retropie on a dirt cheap Pi Zero and that one only has 512MB of RAM. It may depend on what you are trying to emulate (I mainly do NES/SNES/Sega games on mine). If you are trying to emulate newer stuff, it will likely need more umph. I can't speak to the video and music since all my TVs just support that stuff natively now.