If you want it to be as stable as possible, you should update the eeprom with a spare sd card and then boot from usb. I just got one of these to run a smb/minecraft server on a pi4:
And yes, you can dual boot using the NOOBS installer. Then you can install retropie over desktop raspbian and dual boot kodi. That was my previous setup before I switched it to a server.
If you do buy an sd card, buy locally. Amazon had a really bad problem with fake sd cards. Even ones bought directly from amazon can be fake because they get mixed up at the warehouse.
I had the 32GB for a while and it started complaining recently: https://www.amazon.com/gp/product/B07D7SX9NS/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&th=1
I then got the same drive but 256GB, it's faster as well as larger and it doesn't complain anymore: https://www.amazon.com/gp/product/B07D7Q41PM/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1