Cross is Boss. Tons of fun, and it’s great if your local cycling club puts it on with different disciplines. Mine back where I used to live had one for fat bikes, one for competitive cross bikes, and even one for rec mtb bikes. It really let everyone give it a try. As long as you have two wheels and pedals, you could race!
As for tips, it’s not much different than mountain biking other than the skinny tires. So brake before a corner, and don’t lean as much. I also find that running is sometimes way faster than riding, especially those muddy climbs.