I only use plain openwrt with mine, and I’m able to max 500mbps (my isp speed) with it…
Note the cpufreq governer on ipq40xx targets is too slow in response to load, so if you manually set freq to max it will perform admirably, I don’t know if it will max your 1gbps line, but to give you an idea, I get consistent 500/100 on speedtests, and I get near 480mbps on iperf3 runs between the router and a PC on wireless (480 wireless for the wifi isn’t bad… given the ipq40xx platform is only 2:2 streams).
I bought a few B1300s as they seem simple and well built, one disappointment however is the lack of a heatsink that appears in FCC and some pics online:
When I opened up my unit it didnt have heatsinks… given I sometimes really push those routers with many tasks, I would’ve liked it if what I received matched what I found online… but hey, they work fine so no harm I guess.