Is the PR460X fast enough for multi-gig internet?

Yes. It has 2.5 Gigabit Ethernet ports, so it can pass through internet speeds above Gigabit when your modem and cabling support it. Devices on Gigabit ports still run at Gigabit.

Does it have PoE for access points or cameras?

No. The PR460X does not supply Power over Ethernet, so PoE devices need their own injectors or a PoE switch.

Can I attach a USB drive to share files?

No. There is no USB port, so storage and printer sharing over USB are not options on this model.

How many wired devices can I connect?

It lists six LAN ports, mixing 2.5 Gigabit and Gigabit Ethernet. That covers a small office of PCs, a NAS and a few access points without adding a switch.

Is this a good fit for a home user?

Only if you need multi-gig wired links. A mainstream home router is simpler and covers typical Gigabit connections; the PR460X earns its place with 2.5G ports and more LAN capacity.

Does it replace a separate Wi-Fi access point?

It includes Wi-Fi, so it can serve wireless clients on its own. In larger spaces you may still add access points for coverage, and those will need PoE injectors or a PoE switch.