Steam, GOG, EPIC library external ssd

I'm creating a gaming library from the GOG, EPIC, and Steam libraries I have onto my 2TB usb-c ssd.

I assume I can download games from all three stores with no issue to this one drive?

I've been able to load some GOG and EPIC games using a different 1TB usb-c ssd on my Retroid Pocket G2.

I believe the main issue with many games will be DRM?

1. I have GTA V on steam and EPIC but heard it won't run?

2. I have RDR2 on Steam and assume it won't run?

3. I heard Mass Effect 2 worked and I have Mss Effect Legendary in Steam but not sure if it will work or not? I heard keyboard to login or something...?

4. Is is true that GOG and EPIC games can be played odd USB-C SSD but steam won't work???

Any advice as I am starting to DL a few Steam games to the new 2TB USB-c SSD?