5506W has a built in access point.
I think the 5506H is in a hardened case, normally used in industrial environments. A normal business operating from an office should not use this one.
While it mentions Firepower, you have to buy licences for this separately to get it going. So it is more that is the the "capability" to have Firepower.
The unit can do 10 site to site VPNs by default. You can then buy a security plus licence to lift this limit to 50. You can also buy the 5506 up front withthe security plus licence bundled in.