Router recommendation need.

[zMaliz]

If nothing on your network requires UPnP - double NAT your appliance and test again. It will split the workload between the two devices you already have and you may not need to replace anything. PPPoE is single threaded. N100 is much faster CPU and won’t have issues with this speed, but may not be needed.

I do have UPnP enabled for my son's PS5 and XBox.
I also run multiple SIP / VoIP servers and devices on the LAN connecting to remote sites, double NAT may upset that.

 

[Digilog]

Free BSD network stack isn't the greatest and all of these OS on routers does require a little bit of tuning from the typical desktop setting, and yes it does not multi thread by default. However you should be able to set in /boot/loader.conf.

net.isr.maxthreads="-1"

But you should disable hyperthreading because BSD doesn't use it and it will slow things down.

PPPoe requires encapsulation and that is why it takes up system resources.

I don't run this software because they didn't tweak the OS and at the time I submitted what they needed to change, and some of the other devs didn't want to step in and apply it because there was drama they didn't want to deal with. But anyways, getting around character defects of others, I will post the BSD profile for networking >1Gb here if you need it.