TM UniFi Turbo Upgrade 800Mbps SpeedTest - OpenWRT Devices
Pulled out some OpenWRT toys and run some WAN to LAN SpeedTest 
I use OpenWRT mostly nowadays as the main RG (Router-Gateway), then just choose one of my wireless router setup as AP (currently I use RT-AC68U). My immediate test is WAN to LAN traffic to see how's the 800/200Mbps DL/UL SpeedTest performance on these OpenWRT devices, with the following setup/packages :
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Switch Vlan 500+600 tag/untag, Interfaces PPPoE+IPv6, NAT Offloading, Adblock, SQM Egress upload only, multiple DDNS, WOL, Statistic/Graph, etc.
Somehow if I use browser run the Ookla SpeedTest.net, I always get upload test error, so I download and install the Ookla SpeedTest for desktop from HERE.
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Noticed the CPU load is not very high, so I purposely rebooted the device and run SpeedTest immediately, the CPU load does spike (as expected) but still can run 800Mbps, not bad for a really cheap MT7621 toy
ASUS RT-AC1300UHP / RT-AC58U :
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Linksys WRT1900AC :
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Overall I'm quite happy with the result, it seems these OpenWRT devices, from cheapest like the WR1200JS to WRT1900, can max out the 800/200Mbps WAN to LAN speed throughput base on my typical setup/packages 
I might do some AP wireless testing later to determine which AP is more suitable for my environment ...