1. the drops still work at this stage
2. they don't currently work for PS5
3 claiming your drops is not enought you have to actually link them in the Larian system which needs a Larian account linked to your steam or Gog account before it will work in game
the steps for Gog are laid out here
https://windowsforum.com/threads/how-to-get-your-twitch-drops-in-bg3-on-gog.337269/#post-839561
