For your skin, make sure it’s something that doesn’t stick out. Behemoth is a big monster, so using something like Jade skin on Barracks or Dam is a dumb move. When in doubt, Default is best (although I always use my Elite skin).
Perks to pick from are traversial speed, damage boost and maaaybe movement speed if you’re confident about your accuracy.
I, personally, start off with 2 in Rock Wall and 1 in Tongue Grab. If they’re catching up to you, throw up the wall, especially if you can do so out of sight, then roll away - you only have so much time to get away. If they are still on your tail, tongue grab the first hunter to come around, throw up the wall, and give a reason to keep their distance. If they dome you, remember - you aren’t trapped in there with them, they’re trapped in there with YOU. Be confident and isolate the Trapper. Destroy Sunny Drones if they’re present.
Don’t be fooled, Rock Wall can be used offensively. Down the trapper, and roll out of there. Rinse and repeat until you can evolve. Unlock Lava Bomb and Fissure, put two in the one you think you’re better with. Now you’re more ready for a fight. The Hunters may catch you shortly after you evolve, so be ready for that. At this point, you shouldn’t worry so much about stealth. S2 Behemoth is still massive, so you should be ready for the Hunters to catch up to you. Evolve to S3 if you can, and use points as you see fit.
EDIT - Be careful about being aggressive. Bob is easy to kite