It really depends on what is included with the motherboard and the WiFi card you choose. At the high end you’ll certainly find better WiFi cards. But if a motherboard includes 802.11ac and price is a concern. You likely won’t be able to buy a similar motherboard sans WiFi and a PCIe WiFi card for the same price. Which is as good or better.
Also it doesn’t matter if you buy the best WiFi card out there if you router is a piece of junk.
One piece you want to look out for is antennae with a base and wire leads. Antennae sticking out the back of the case are prone to a lot of interference. It is best if they are away from the case. In such a manner that the case is not between them and the router.