As far as OBS....tried it...works...clunky interface IMO. Nvidia shadowplay utilizes inherent GPU capabilities to reduce impact on performance....which, since OBS is agnostic, I'm not sure is present in others.
That depends on the OBS codec you choose. If you choose NVEnc, as I mentioned, it uses the same video card tech that Shadowplay does to offload the encoding to the GPU. Except you can configure everything, instead of just what Shadowplay lets you configure. NVEnc is only usable if you have the right kind of Nvidia graphics card installed, it is
not video card agnostic.
And the interface for OBS is much improved in OBS Studio instead of OBS Classic. They only recently updated the web site to lead people primarily to the better version.
Like I said, if you can't be assed to figure out any settings, then (keep on using) use Shadowplay though, as it works for people without requiring them to know very much.