@steptoe said in Booting from SD Card with SSD Storage vs full SSD Install:

You DO have to leave the SD card in though, as it reads the boot sequence from the SD card before passing all control to the external SSD or hard drive

No, that's not required on the Pi4.

Roms (and saves) can be easily be placed on an external disc - https://retropie.org.uk/docs/Running-ROMs-from-a-USB-drive/.

For configurations (almost all of them are kept in /opt/retropie/configs), there's no out-of-the-box solution available, since they require a Linux filesystem and generally users have a PC/macOS compatible partitioning schema on their external disc.

If you want to dedicate a SSD just for running RetroPie, you can just install RetroPie on the SSD drive (same process as installing it on a sdcard) directly.

Has anybody ever came across a good learning book for this stuff?

RetroPie specific documentation - https://retropie.org.uk/docs/. Raspberry Pi documentation - https://www.raspberrypi.com/documentation/ (has a Getting started section and a Using RasPI OS guide). The RetroPie image is based on RasPI OS. For Linux in general, I'd recommend the Debian user guide (https://www.debian.org/doc/manuals/debian-reference/index.en.html). RasPI OS is based on Debian, so it should apply to a RetroPie installation.