If your that concerned about network security, don't use consumer level based wifi routers in the first place. Also a complete waste of money on AX86u to just sit there as an AP
Depends on what devices you are connecting and the surrounding environment/obstacles. Are you maintaing 2.4ghz/5ghz devices or only one type? What throughput are they gonna need? Are you pushing stuff over a VPN via wifi that will be latency sensitive like real time video?
This is the smallest Netgate device capable of running pfSense and it's processing power is actually less than AX86U's own router part. Get SG-5100 or Qotom box instead with mobile i3/i5 CPU and min of 4GB RAM. Today you want pfBlocker, tomorrow you'll want Snort/Suricata or fast VPN. SG-1100 is good for basic configurations only with about 500Mbps ISP.