I’ve taken JSX from Orange County, CA (SNA) to Oakland, and Oakland to Vegas. Super easy and convenient. Showed up 45 minutes before the first flight and 30 minutes before the second flight. Walked in, showed my ID to get checked in, gave them my bags, got swabbed as part of security check, and had a short 20 minute wait in the lounge. The Oakland lounge was lacking snacks though.
And the prices were really good, $79 for each flight. The prices are really good if you can book ahead of time.
They also let you do standby to an earlier flight if there’s space, my friend did that.