When it comes to compare different Cisco wireless product here is the best place you should go for.
It lists all the supported feature of each product in a manner you can compare with related products easily. Certain features like client count per AP is documented here which is rare to find even within a datasheet. If you want to see what Cisco AP model support 802.11ac, you can find it easily as 3600, 2700 & 3700 series.
Here is the snapshot of Indoor Access Points, Outdoor AP & WLC comparison tables available in be above link.