A6150 speeds not highter then 585 mbits

WiFi adapters as well as APs, are rated on the PHY rate of the WiFi standard. While speeds can vary based on location (WiFi noise floor and available airtime), a PHY rate of 867Mbps, will often yield a real world throughput of around 600-650Mbps under good conditions, not too far and not too close to the AP.

Speeds can end up lower if multiple clients are connected, even if they are generating very little traffic, especially if there are mixed client types. For example, an 802.11n 5GHz client on the same AP as a 802.11ac client will have a lot more overhead than 2 802.11ac clients on the same radio.

If the PHY rate is low while you are close to the router, as 585Mbps PHY rate would indicate the client using 64QAM rather than 256QAM, then it could indicate other issues. For example, is the adapter on a USB port that is close to a very RF noisy device? Is the USB port in a location where it is surrounded by a lot of metal or other USB plugs where the grip part of the plug is effectively a large RF shield?

The A6150 WiFi adapter is designed to be very small, but due to that design, the core components are all inside of the portion of the plug that inserts into the USB port (providing shielding on all but one side), then the plastic part is essentially there to house the LDS antenna (designed around being very omnidirectional)

Beyond that, the A6150 has full support for 2 stream 802.11ac at 256QAM, 5/6,  GI 400ns, and will not really drop the rate unless it is experiencing many frame re-transmissions.