I've bought an Archer C7 V2 for cheap and it's working great (2.4Ghz and 5Ghz), however I've found out about QoS recently and I want to give it a go along with OpenWRT (I have a 50Mbps connection, so I should be fine with this hardware). Reading the wiki, I see that this router is well supported, but after a quick search in the forums I saw a lot of posts complaining about wifi stability (specially 5Ghz) and it held me back, however, most of them seems outdated.
So, how's the stability of it right now? As I'm working from home, I rather live with the stock firmware without QoS then having QoS and unstable wifi.
I have an Archer C7 V2 device and, as far as I'm concerned, it's a good product. I loved using OpenWRT because it allows for so much flexibility and extendability. I used my Archer C7 as an AP combined with OPNSense to have a full-fledged firewall/router/AP combo. However, a lot of the complaints about the 2.4GHz band were true - after a while, the router would seem to stop working and needed a reset. I ended up setting up a CRON job to reboot the router every morning. Still, with the CRON reboot, it still ended up being a solid router.
I found that pre-built images from the download site worked better than some of my custom builds - I recommend staying with those.
Since I have a few IoT devices through the house, I ended up buying a Mesh router system as my WiFi AP and now use my Archer C7 as an unmanaged switch (with WiFi turned off) for wired computers.
My overall assessment: Archer C7 V2 is a good product. With OpenWRT, you'll tinker with it but it's still a good product.
I have ten archers up and running. Mesh via 5ghz and 2.4 and 5ghz access points, serving wifi for multiple vlan's. They work pretty well if using non-ct drivers and batman-adv, wpad-mesh-openssl. Loving those cheap and good pieces. They peak around 400 mbit/sec max throughput (in bridge mode, no nat, no wan routing). The latest openwrt 19.07.x has a bug regarding preserving of large files during sysupgrade (spi nor reads need to be handled correctly by the kernel). So I've made a custom oprnwrt 19.07.4 build from the official source including non ct wifi drivers, wpad-mesh, batman-adv and usb mass storage support . I have 2.4 dropouts very rarely under high load with many clients, but this is solved by my watchdog script. It reads the syslog from the ap continuously and restarts the driver if it fails.
In my experience it is other way around. 5GHz is flawless, but 2.4GHz is flaky, especially with many clients/devices. There is this hearsay that swapping out 5GHz drivers will make 2.4 behave but I never got 2.4 to work well. So I just run 5GHz (have multiple C7's acting as Access Points) and everything has worked well ... typically hundreds of days of uptime.
I have been tracking RAM usage on my C7's and this is not really true. I run mine as AP's so they usually have more than 70% RAM free. Despite having lot of free RAM, 2.4GHz will hang after a while, regardless of ath10k drivers (or lack of, I even tried removing them).
I had the same "hang" Problem a few month ago. Since then my Archer C7 v2 runs very stable. I use 2.4 and 5 GHz, Version 19.07.4 and ath10k-firmware-qca988x-ct. I have no idea, what have caused this instability.
Longtime Archer C7 V2 here. OpenWrt 18 series works well with this router, but you need to consider that OpenWrt doesn't support the hardware switch on this router, so you are limited by the CPU of this router. Sharing with 5 or 6 users is just fine, but more than that, you will probably need to reset it every few days (or every day if you're using OpenWrt 19 series.). QOS can handle 50 Mbps just fine (Mine handled up to about 300Mbps with no probems. Anything beyond that will be beyond the CPU power of this router and you will experience problems)
I never got this router work consistently with the 19 series: Random disconnections, random freezes , random Wireless problems, dropped packets... In the end i just reverted to original firmware and i'm using a RPI4 to handle QOS, print server and a pendrive as network drive.
In your case, i think the best is to keep using the 18 series. Still stable and quite usable at your internet speed.
Interesting. Are you sure about this? I am using multiple C7's as combined "edge switches" and "AP's". All of them are wired to central router (thru WAN port, I untagged the ports so it is basically just a 5-port switch now) and have various stuff connected "locally" (on LAN1-4). Just for fun, I run iperf3 from LAN to WAN1 port (wired, PC to PC) and hit 900Mbit/sec w/o issues.
To my knowledge, is is fully fledged hardware switch and my measurments support that.
Sorry, my bad. What is not supported is the "hardware NAT" (a.k.a. "Qualcomm FastPath" or "hardware flow offloading"). The Atheros QCA9558 processor is more than capable to route 1Gbps in software without major issues (Except the often reported 1.9x cpu usage from the router logs...) . Where problems arise is when the number of concurrent clients connected (in my case at least, YMMV) are more than 10 (See my post with details here: I need help on a router). The 19 series in this case was never stable on my case. The 15 up to 18 series was pretty OK to me (But, back then, i didn't had to route 500Mbps to more than 10 clients ), but since i have to manage around 12-14 clients, i need QOS and is QOS what makes things slow in this router.
I believe your 2.4 WLAN is failing and you are mixing it up with "router" failing. In my experience, only thing that will "fail" in Archer C7 running OpenWRT is 2.4GHz WiFi. On my routers, 2.4 always failed after couple of days using multiple clients. On 18.x and 19.x versions, using different ath10k drivers, using no ath10k drivers at all etc. It never ever worked right. It is now disabled and I consider it faulty.
Routing/NAT always worked fine (within CPU constraints).
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.