Yeah, I've seen big box. I found launchbox when I was trying to set up retroarch on my brother's laptop for him last Christmas and it kept giving me a ton of errors. I'm personally not a fan of the popout emulators, I much prefer having everything contained in a simple way like retroarch.
I have actually seen that recording setting in retroarch before but I forgot about it. I didn't know you could use it to stream though. It's still not that useful for my needs unfortunately, as I would also need to capture other programs outside of retroarch whilst recording/streaming. Being able to capture mic audio and having something similar to livesplit inside retroarch for recording would be amazing. It makes me wonder how difficult it would be to get something like that to work.
That UI reminds me of a paid emulator frontend called launchbox. I guess it is pretty useful, but personally I like being able to flick through everything with a controller without switching back and forth with my keyboard. I would probably use Retroarch for everything, but unfortunately it has some severe lag issues when I capture it with recording software, so I need to use separate emulators for that.