Gotta love the deceptive patterns :-)

  Currently RARBG primary domain is:
  https://rarbg.to (actually links to https://rargb.to, note the bg/gb)

Because that's not rarbg, rarbg is "rarbg.to", not rarbg.tw, rargb.to, rarbggo.to, rarbgproxy.to, rarbgmirror.org, rarbgaccessed.org, rarbgget.org

but what's difference between rargb.to and rarbg.to ?

rarbg.to is the real rarbg, rargb.to isn't.

The recommended torrents aren't actual though, some things are not working.