Bittorrent client + Media Player + Retropie?

Hello guys,
I have a pi 0w running the latest dietpi with transmission and xfce.
I want to be able to play some times movies from my HDD or USB flash drive and play NES games.
The question is, if I install from dietpi-software Retropie and Kodi, will I be able to switch between those three? If yes, how?
Is kodi the best option or there is another better solution in the software list?

PLEX might be an option…but not sure how well it can encode video’s on the fly (due to somewhat limited processor power). But it can host network media (think personal netflix)

I would like to keep desktop with transmission and select between those three.
Like if I want to play a movie, I can reboot the pi into KODI and after that return again on normal desktop.
In first I thought that if I install KODI and Retropie this would happen if I switch DietPi-AutoStart but then if I boot somewhere else than dietpi I don’t know if I will be able to return back to it. Any suggestions?