The pfSense installation (FreeBSD inside it with all the pfSense code bundled together) is very small also. Fits in 1GB. You only need the smallest SSD, unless you are planning to use a proxy cache package and want to cache ginormous amounts of stuff.
Unless you have bucket loads of interfaces, rules, aliases with millions of entries, proxy cache that you want to keep in-memory cache of lots of stuff,… there is no point in adding more RAM.
Use the 64-bit install anyway on 64-bit capable hardware. All the packages work on 32 or 64 bit installs.
You can create VIPs on WAN for extra public IPs, forward those inside to wherever you like. That is in the standard install.
OpenVPN is part of the standard install. You can easily set up a Road Warrior OpenVPN server. Then give it the pass rules that you wish to allow Road Warrior access to whatever inside LANs or hosts/ports you wish.