I did something similar. I used Proxmox and then installed PfSense as a virtual machine. You might want to look into OPNsense and PfSense. There are addons for both that do the same as AdGuard and are free and open source. I had good experiences with pfBlocker

Guess I’m continuing to use Firefox in hell then

Geekbench is pretty useless for actual performance comparisons.

Not sure how it could help me solder or find faults on PCBs.

That seems strange I’m running a pfSense VM on proxmox with a Core i3 5010u. The VM has 2 cores and 1GB ram and I’m getting around 500 Mbit on my Gigabit cable in download. I only disabled hardware checksum on the pfSense side. What CPU exactly do you have? Also make sure to set the CPU type for the OPNsense to „host“. That helped quite a bit for me.