I have Pillars of Eternity on Steam (the base game).
I have Pillars of Eternity on Twitch (the Definitive edition).
I don't like using Twitch for games that aren't super short "play and forget" types, definitely don't feel like playing long stuff with it (since it hasn't even cloud saves and I know myself, I pause and continue games all the time).
Was waiting for some way to get the White March DLCs cheaply on Steam, but recently I had an idea:
What if I install the game on Steam, and copy the Twitch version over it (not replacing anything, essentially just the DLCs).

I haven't tried it yet, since I don't plan on playing it right now, but someone on the Steam forums had the same idea and it actually seems to work.
Nice~