I had a very interesting boarding experience on an SFO-SAN flight recently.

The flight was 100% full, and they kept calling out over the PA asking people to gate-check larger carry-ons.

They call pre-boarding, small children, disabled, etc.

They then called First / MCS.

Then they called anyone who had already gate-checked their bag.

Then they called anyone with a non-rolly-bag!

Finally general call for everyone else with large carry-on.

That was the first time I had ever seen such a sequence. Luckily I had packed light.

P.S. on all previous VX flights boarding was done back of plane forward. YMMV.