A multistream chat overlay: all four chats on screen as one feed, using a browser source. No plugin, and nothing to install in OBS.
Open the overlay builder from the app. Enter your channel names, then adjust the appearance while watching the live preview. The preview sits on a checkerboard so you can see exactly what is transparent, and you can switch it between a bright scene, a dark scene and a green screen, because an overlay that reads well on grey often disappears on white.
Position and resize it like any other source. The background is transparent, so only the text appears over your scene.
OBS caches browser sources. If you change your settings and the overlay keeps showing the old look, right-click the source, open Properties, and click Refresh cache of current page.
No. It is a browser source, which is built into OBS. Paste the link and it works.
Yes. Any broadcasting software that supports browser sources can use the same link.
Yes by default, so only chat text appears over your scene. You can add a background colour and set its opacity if you prefer.