PPPoE Speeds

I currently have a Purple SE and have recently upgraded to Full Fibre 500/75 in the UK PPPoE connection. My Purple SE is maxing out about 300 down on ethernet connected PC. Is this the limit for PPPoE on the Purple SE?

Also do we have a current list of PPPoE speeds of the Gold series Firewalla's? I am lookint to maybe get Gigabit at some point.

Thanks