I really like Abus nufix to lock wheels and seatpost. Seatpost is less necessary. Compared to other locking bolts, the housing spins so there’s no way to get purchase with pliers. I keep a small wrench in my tool kit to remove the wheels when needed.
In addition to that I use a kryptonite lock and make sure I attach it through my bike frame and something really solid. If you try to lock to a sign, try to pull the sign out of the ground first and maybe check if you can use your fingers to remove the bolt. I like kryptonite because of their insurance program but there are plenty of solid lock brands out there. I’ve had good luck with Abus and Axa as well.
Lastly bike index , project 529 or a similar local org can act as a deterrent or method of getting your bike back if it’s stollen. I’ve got bike index stickers on all my bikes.