Recently I've had the problem that my streams on Twitch are always extremely lagging when I'm online with a friend on Discord.
What could be the problem? Basically I didn't have the problems before.
If you talk together in a voice channel, you should make sure that the voice quality is turned down. It is probably pulled extremely far to the right with you, which means that the voice channel eats up a lot of the Internet.
Edit a channel, it looks like this:
You should pull it to 64kbps.
I also know from others that sometimes the "Activate high QoS packet priority" function under Settings → Language & Video can play a role in something like that.