Go into the Streaming settings and switch it to Record then configure other settings accordingly. Youtube will compress your uploads to hell, but the more "raw" the file, i.e. the less already compressed it is, the better the video will appear because double compressing magnifies artifacting.
You can't use shadowplay on AMD hardware anyway, so no worries there.
Another, very important thing to consider is your capture hardware. What is your budget? (these are also useful for capturing live camera feeds from a DSLR or camcorder for quality facecam)
Dual output to a blackmagic card or the new Av.IO USB3 devices is good, using AMD's hardware encoder works well, but you'll sacrifice both quality and source bitrate if you go that route
Ideally, (Read: if money is no object) you'd pipe your native output into a seperate capture rig and composite/stream from there, but as you're going with ryzen, I think you'll be fine on a single tower, at least for the time being
Links to referenced cap hardware:
Ignore the negative reviews on the blackmagic product, they're from Dew™ chugging teens that wanted bundled bloatware "like their elgato has" for the most part
mine's worked flawlessly since I got it, and with a little tweaking it'll work in linux too
As someone, who runs his YouTube channel on Athlon 760k and R9 270X I can't record with OBS. Gameplay is awful. Mirilis Action is what I will recommend. There is absolutely no noticeable difference in game between playing and recording... https://mirillis.com/en/products/action.html There is 30 days free trial, so you can try it out... No need for external peripherals and devices.