Mikrotik Hap ac2, optimising wifi perfomance

Hey Guys,
I recently installed Openwrt on Mikrotik hap ac2. I was looking for a travel router and this is very compact so I went for it.
However, I see that the wifi perfomance is not very good. I get less than 260Mbps within lan using Iperf3.
I am not able to stream without lag 20Mbps files over my remote Plex server. (I am able to when directly connected via lan.)

Some other info:

  • Using 80MHz in 104 channel.
  • Added country code to my country(IN)
  • Power: tried 3 12, 16 DBi. Throughput's almost same when nearby.
  • I have enable packet steering and software + hardware offloading.
  • I tried using irqbalance. Not sure if it works. Although, I think that 250Mbps in LAN is too low. There's should be something else that I am missing.

any help to improve performance is appreciated.