Nope, stock firmware works just nice for 2 weeks, no restarts, no wifi problems (no wifi interruptions, no IPTV freezes, no router freezes, no stuttening on games, no loss of connection between my RPI3 improvised repeater (19.xx had a lot of them for me, Openwrt 15 up to 18 worked great for me (although at the time was for 100Mbps, YMMV)). The problem is not the hardware. (At the very least, not in my case, although the router is being used as a dumb access point, the heavywork is done on a RPI4).
QOS?, That's what you need when you have around 6-8 clients using the internet at the same time in the night, with at least 2 of them doing torrents (i am one, and at the same time using netflix, and doing some light M$VPN Sessions to the work), other uses a Kodi box using IPTV, other plays fallout 76 (WTF!!??... oh well, i don't judge... too much ) and there's another that does remote work using remote desktop clients. Not counting phones, or spotify, that the least of the problems. That's explain why they are paying more for the connection, but also the need for a better QOS manager, that's why, in my case, i use a rpi4, since i couldn't find a better router with OpenWRT support in my country. (Chile). Kinda bumpy supported nowadays, but better than what i had.
Then again, i think the OP would be more than happy using the 18.xx series for what he got. The Archer C7 is more than overkill at that speed. And at least from my experience, stay away from the 19.xx series. The headaches aren't worth it.