I am currently playing with my old TP-Link C2600 running openwrt 19.07.2. The wifi speeds max out at about 170 Mbit/s. If I use a self-made build with the non-ct drivers, its nearly twice as fast. I was wondering wether I need some specific tweaks for the ct-drivers to get to "good" speeds???
Any suggestions what I can try? I am using a MacBook Pro that reaches up to 500
Mbit/s using my other router Xiaomi R3P running openwrt-19.07.2.
@thorsten97, thank you so much for bringing this up, I though I was the only one having this problem.
Device: Archer C7 v2
OS: Stock OpenWRT 19.07.3
Driver: ath10k-ct
Firmware: 10.1-ct-8x-__fW-022-b0e1b7cd
Software flow offloading: enabled in settings in all cases described below
With the setup above I get around 200 Mbps max while at the same time on a custom build with ath10k non-ct I get around 2x as much. Changing ath10k firmware doesn't affect the speeds with both drivers. I also get the same low speeds with the same custom build but ath10k-ct drivers. I presume the problem lies within the drivers themselves.
However, I should note that non-ct ath10k drivers are quite unstable in my experience - I observe random and sporadic packet loss with various devices (smartphones, laptops) - sometimes momentarily and sometimes lasting literally tens of seconds - after they have been connected for a few hours. Reconnecting the client helps and the connection becomes stable for some time again but it is very annoying to do that multiple times over the day. Because of that, I had to resort to using the stock OpenWRT with halved speeds 
I hope someone can give us a hint about why the -ct drivers can have this speed issue.
Mine is working fine. I have the Ubiquiti AC LR with ath10k-ct and non-ct firmware. It reaches nearly 500 Mbps (its limited by the CPU). Tried all combinations possible with the ct and non-ct, and the one i said at start it's the best one for me (just 20-30 Mbps more than others).