I used to do these from time to time. They are pretty fun and safe but they would be a lot more fun if traffic on 15 wasn’t so bad. Augusta is a perfect way to dip your toe into the James Brown Celebrity Hot Tub of crit racing.
I’m sure many people have written better “intro to crit” articles but my basic advice is to just line up figure it out as you go. Keep your head up, your ears open and your brain on.
Aside from that, be ready to pedal really hard for short periods of time. Cat 5 racing is defined by wild power surges followed by periods of indecision, awkward swerving and shouting..like prom night but without the regret.
If you’ve not done a lot of fast group road riding and aren’t comfortable riding in close company there a good change you’ll get dropped. It’s ok. It happens to everyone eventually so might as well get it out of the way. The officials will give instructions at the start line but in these races they typically let you rejoin the race on the next lap if you get dropped provided you don’t contest the sprint.
AFAIK disc brakes have never not been legal in USAC road racing.