Now that there is a Raspberry Pi4 supporting USB 3.0 and having a Gigabit Ethernet port I am considering buying one and re-using it as an Access Point with a USB WiFi card with external antennas. I am wondering if I will need an external USB hub to power the WiFi card though. So far I have tried to do exactly the same with Raspberry Pi 3B but the problem was that the USB port was capped to USB 2.0 and also the USB hub was shared with the Ethernet port, so it wouldn't make much sense. On top of that, I was using some card which was drawing too much power from the USB port and was dropping the connection constantly. If I am not wrong the maximum current the USB-2 ports on the RPI 3B is 600mA and apparently, this card was pulling more than this 600mA current.
Can you also recommend me a chipset with good Linux support which also supports AP mode in Raspbian, preferably AC-1200 or more and MU-MIMO support in the kernel of the latest Raspbian Buster?
I have tried to look into https://elinux.org/RPi_USB_Wi-Fi_Adapters but the information there seems to be a bit out of date and not very accurate.