150mbps on wired connection, 50mbps on Wi-Fi

WMM is required on the router for wireless clients.. Leave it enabled on the router. The router's capability and the wireless client's capability are two different things. Sounds like you are probably using a phone. Speedtest is hit and miss IMO. I see about the same on a phone with speedtest. Ensure your wireless client has the latest drivers. For 2.4ghz choose 1,6, or 11 as a channel. For 5ghz try using the higher channels. You probably have to try more than one channel to test, as not all channels are equal when it comes to finding the best channel for a wifi client. Nor does every wireless client respond the same to every router.

Also, check to see if there are any firmware updates for your router. If there is, after you install the update, ensure that you reset the router to factory default, then reconfigure. Also, change the router login password and the wifi passphrase from their defuault passwords.