If you wish to try use @ACwifidude NSS enabled build. I recommend you first try his latest master branch. This one has ath10k driver/firmware
R7800-20220926-MasterNSS-ath10k-sysupgrade.bin
Then test the WLAN performance with iperf3 server and client. Server to be run on wired computer connected to the R7800 switch. Search for details on the same thread. There are many posts about it.
Probably the version you currently use has ath10k-ct driver/firmware which is default for OpenWrt. I couldn't get good results with this driver hence I use ath10k.
Another "wrong" thing that I've found is that for ISP speeds of 100Mbps and below the Speedtest results are really inaccurate. Even on 5GHz the test gives most of the time only 50-60Mbps.