You can easily put the username and password into a file, store it in /root for example with chmod 600 so that is only readable by the root user, and reference it in /etc/fstab with credentials={filename}
Ya, the PA120 is a couple bucks less than when I bought one last week. Also the PA120 has the ARGB fan version if you are into that. (I am.) I was also able to buy 3x matching ARGB fans for the case for $12.
I'm running OPNsense (as of late January) virtualized under Proxmox on an i7-7700K and it's been running well. Scored an Intel X540 and a Mellanox ConnectX3-Pro from eBay and OPNsense can download and upload at 5 gigabits with my ISP. Also pulls very little power. Maybe 50 watts under load...
I kinda want to get the SE version because I have some 10g but I don't want to invest that kinda cash into it and one or more APs for my house. I think the lack of configuration options in the firmware would annoy me in the long run.