With a server you don’t need to do the implicit oAuth redirect to Twitch, as you’d be using regular user oAuth and you’ll have a refresh token to use.
And if the regular user token cannot be refreshed via it’s refresh token, the broadcaster can do the reauthing “off stream” without having to right click the source in OBS and selecting “interact” and doing it visibly on stream.
And usually the token cannot be refreshed when the broadcaster has changed their twitch password or removed the app link for some reason, and since it’s done in the normal browser, the Twitch cookies/session should still be valid due to natural use of the Twitch website, unless the browser source where theres no natural website usage.
And using a server if the relogin to Twitch is required (which it shouldn’t if the streamer has logged in to go update their channel title etc, the caster won’t leak the length of their password and/or when the login to your tool you can present news/updates if needed, some of which probably don’t want to be visible on stream and/or provide the control panel.
I kinda rambled a bit there.