As far as I know, you still can't upload video to Twitch: they are focusing on livestreams. You can record your livestream, and then make it available to view, but well edited videos are rare (you'd have to make and edit the video, then stream it, then edit the VOD for length, etc)

Edit: found https://help.twitch.tv/customer/portal/articles/2577667-vide... which seems to indicate that you can upload video, but it seems to be rare on the platform compared to their bread and butter livestreams.

YouTube is still the king of "Let's Play" and edited-walkthrough formats.