RetroPie is a fairly nice package. It includes the RetroArch emulator/front-end with a fairly nice skin to it. If your objective is playing some older emulated titles, it will pretty much do you proud. And a Raspberry Pi 3 should have all the power you need for most of the available emulators. You might start to see some performance hitching once you get into the PS1-era consoles. But I've tested RetroPie on a Raspberry Pi 2 and had great performance for Sega CD titles. Anything prior to that should run great.
When you refer to "setups and ideas" I'm assuming that you mean the physical application. RetroPie itself handles most of the software side of things. For a physical setup, I would say either make a custom console, or rig up your own mini-arcade. I made a custom console for my brother a year ago, and had a lot of fun doing it. I was able to rig up LED-buttons for the power, reset, and blue-tooth setup. It took a little bit of coding to pull off, but it was all in Python so it wasn't that difficult. Wiring them up to the GPIO pins was nifty.
If you are a bit more ambitious, you could create a custom arcade setup, with the arcade controls wired directly into the GPIO pins. This takes a little more doing, but is entirely possible.