optimal Wifi setting for RAX20 ?disable AX

Hello all, I recently perchased a rax20 and using FTTC NBN. When AX is enabled I experience continuous drops in performace. When disabled the network is fast and snappy. Why is this? Isnt the whole point of Ax to have Wifi6? I know that many new devices will be wifi 6 enabled so I want to get on top of this. 

Cheers