There are enough YouTube videos out there that prove Cat 5, Cat 4/5 and Cat 4 races have some very fit, strong and motivated riders in them. Sharpen up their handling and they’re Cat 3, maybe even Cat 2 material. Lower level races and the racers are no joke.
Staying towards the front is the dream. Every new racer has been told that the top 10/15 positions is where it’s safest, easiest etc… Getting there and staying there is a whole other ballgame.
As I’m sure others have said, set yourself a couple of pre-race learning goals. How do you feel moving up/through a pack? How do you feel when you’re cornering at speed with a rider on your inside? Give yourself the opportunity to experience these things. As you progress up the ranks, you’re going to be exposed to these things, regularly.
Above all, have fun, wear a smile and be friendly. There might be other new racers at the event. Make some friends. You might be racing with and against them for years to come 