How fast do you want the VPN to be? What technology are you using, OpenVPN, WireGuard, something else?
What is driving you to put the conflicting goals of security (VPN, firewall) with file sharing and a web server on the same box, one that is directly exposed to the Internet?
With no budget, you should have at least two or three devices (firewall, VPN, containerized web and file sharing), a managed switch, and a wireless AP.. None except the last are an all-in-one router.
(Edit: Marvell wireless drivers don't support 802.11s mesh, at least last I checked. Three-radio devices have advantages for mesh when wanting more than about 1/3 of the channel bandwidth.)