TP-Link actually has quite a few(not the newest models though, but the not-newest-model should work for 95% of the customers) that runs openwrt well.
All my routers are running non-vendor firmware(e.g. openwrt) for the last 15 years, never had any troubles.
At home we connect to a TP-Link Archer C7 running OpenWRT. It's only WiFi5, but we have zero issues streaming many 5ghz devices off of it. It's even held up fine while we both work from home.
I also run a second much older TP-Link router using stock firmware on a separate subnet. I don't think OpenWRT supports that one. But only my IoT devices and smart TV connects to it because I don't trust them on my network anyways.
All that being said, I wish there was something better and easier for the tech illiterate. The state of routers/security/privacy sucks today.
I live near main street in a small touristy coastal town, and there's tons of access point beacons flying around. I only have a 10,000 sq. ft. lot and have three access points to cover it. I turned off "legacy" rates everywhere I could so hopefully all my beacons are 6Mbps+ with greenfield preambles.
Different wifi chipsets cope differently with congestion. Specifically, when packet collisions do occur, some chipsets miss both frames, while other chipsets successfully decode the frame of higher signal strength as long as there's enough of a difference. In low congestion areas it doesn't matter since packets rarely collide, but in high congestion areas it can make a big difference for throughput as packet collisions occur frequently.
I also wonder if it's luck of the draw with some of these cheaper routers? My C7 is also a newer variant, a v5 I think.
And yes, it overheats, especially in sustained transfer.
Slap a heatsink on all the chips and call it a day :D