Before purchasing a POE switch, you'll need to figure out how many devices will ultimately ending up needing POE power, and you'll need to figure out how much POE power you'll need, by adding up the anticipated wattage of each device.
Now, to obfuscate things even more with some hypotheticals. . .
So, let's say you have 3 access points, and the manufacturer's datasheet says they are 12 watts each. Perhaps you end up with 6 POE cameras, that claim to need 5 watts each. You'd need a switch that can supply at least 66 watts of POE power, and has at least 9 POE ports, in addition to an uplink port to connect to your network, and possibly a port for your NVR.
POE ports typically come in multiples of 4, and switches can either be exclusively POE, or a mix of POE and non-POE ports. You'll find various combinations out in the wild, and with varying POE budgets.
Once you exceed 8 POE ports on a single switch, many will have cooling fans, so you may need to take noise into consideration when selecting a switch.
You'll also find that switches with more than 8 POE ports will either be fully POE, or half-and-half.
In our example above, we need 9 POE ports. Since they're usually in multiples of 4, that would indicate a switch with 12 POE ports. But, there aren't alot of 12-port POE switches out in the wild, so you'd either end up with a 24-port switch where half of the ports are POE, or a 16 port switch with full POE.
My first thought would be a 16-port full POE switch. That would cover the 9 devices in the example, plus an uplink port, a port for an NVR, and would leave 5 ports available for expansion. In the example, we were at 66 watts, so something like a TP-Link TL-SG116P, which has a 120 watt budget would certainly meet those needs, and have some extra available power if you add cameras or other POE devices. Yes, it will have a fan.
Don't want noisy fans? If you're not going to expand past 6 cameras and 3 access points from the example, then get an 8-port POE switch with at least a 40w budget, plug in your cameras, your NVR, and an uplink cable to your router or main network switch. Then get a separate 5-port POE switch with at least a 40w budget, and use that strictly for your 3 access points. Enjoy your fan-free living. :-)
Other comments:
Try to avoid no-name brands. Brands that I'd trust, in no particular order: Ubiquiti (some are expensive, others surprisingly affordable). TP-Link. TrendNet. Zyxel.
Try to choose POE+ switches (802.3at), in case you end up with access point(s) that exceeds 15 watts.