I have a bunch of b20x’s in the field. I also never use them on gigabit connections because they aren’t really a true gig router.
Basically, the 1Gbps throughput is for the device in its default state performing only (and ONLY) stateful routing.
Each feature enabled on the router reduces its throughput. In my experience, with all features enabled, stateful routing caps out around 300Mbps.
Your biggest offenders are VPN, QoS, and enabling anything on the Content Blocking page.
If I want to hit gig throughput more comfortably, BR1 Pro’s are considerably more powerful. If I’m wanting to chug a gig pipe all day with all features enabled, I use a Balance 310 5G’s.