Actually have this problem on both an XPS 8500 and 8700. Both running W10.
We just upgraded our ISP speed from 100Mbps to 400Mbps.
One of the PC's, the 8700, can connect wired to the router and reports back 480Mbps down, but when using wireless it reports 270Mbps. On the 8500 only wireless is possible, same 260 or so speed.
Here is the ROOT problem. Different USB devices, one AC1200, the other AC1900. Connection speed on the 8500, 867Mbps, 8700, 1300Mbps... BUT each shows that it is running on a USB 3.0 port (I verified they are in the BLUE ports) but operates @ USB 2.0???
These both have RealTek chips, on RTL8812AU, the other RTL8814AU. I also have the RealTek Wireless USB Utility. Interesting Status Page:
How can this happen?
Do I really need to BUY a PCI card to achieve USB 3.0 support?
Re: USB Wireless Adapter provides low Internet Speed?
There is a big difference between theoretical and actual speed. I think you are doing pretty good. There are many factors that affect WiFi speed, if you want the highest reliable speed use a wired connection.