The router Netgear R7800 Nighthawk X4S AC2600 is marketed with lots of bells and whistles:
MU-MIMO
Beamforming+
Quad Stream Wave 2
Dynamic QoS
On my current setup (with Archer C20i) I have OpenWRT with custom sub-networks for my security IoT. But I have wifi issues.
My main goal in switching to the R7800 is reliable wifi connections and my house is big and all concrete.
But, ultimately, I can leave the sub-networks custom config in my current router and only move the wifi AP to the R7800.
So question is: Will installing OpenWRT on the R7800 loose any of those marketed features? (I've found that OpenWRT is not much feature marketing oriented and understandably.)
The main difference would probably be losing hardware offloading to the NSS cores, which reduces the maximum throughput the r7800 can achieve - as long as your WAN connection speed is below the limits of your ARMv7 cores, that shouldn't be an issue.
QoS is not preinstalled, but installing SQM probably offers you an even better solution than QCA's proprietary QoS (streamboost).
The r7800 is very easy to install - or to revert to the OEM firmware, so the only sensible approach would simply be trying it yourself (just give yourself a week or two to cater OpenWrt's configuration to your needs --> SQM).
and all that is proprietary software/drivers that is not available to opensource projects like OpenWrt, you might have better luck with projects that have access to the proprietary software/drivers like DD-WRT-
Although the wifi part of the "bells and whistles" are mostly marketing wank so yeah it's not a massive difference.
The only real loss is the hardware accelerated QoS, but that device's CPU is strong enough to run OpenWrt's SQM (the QoS feature) up to a 600 Mbit internet connection or so.
If your current router is doing well apart from the wifi I would just buy a simpler and cheaper wifi AP that is supported by OpenWrt and use that for wifi only. Or more than one. With a couple $50 devices you can get a long way and still save more than half the price of that router.
Because no matter all the wifi marketing wank they add to a single device, you can't beat placing more APs in strategic places.