So a quick search of that device shows many refernces to saying in theory it can handle 200 devices but recommended to be limited to 15 per AP. Obviously you are already above that so it may not be to much of a concern. Would be nice to know how they determined that dramatic difference.
One thing of not though is the devices only uses 100mbps uplink if using wired backhaul. So you can't depend on the AP speed spec to determine speed limit. You are really limited to 100mbps.
Depending on coverage needed you could potentially get a Unifi 6+ AP for just over $120 and get allot more capacity on a single AP. They are fairly cheap as well. Ofcourse if it is working for you not much push to spend that money.
If all it is doing is IOT stuff then perhaps. but if anything else is happening on those AP's it could get full quickly.
I would just keep an eye on the devices for odd disconnects or devices offline without explanation. I started to have random devices being offline at times unexpectedly.
My setup is similar. I have 2 APs (Unifi AC Pro). My IOT network is 2.4ghz only and uses 20Mhz channels (1 & 6). I currently have almost 80 IOT devices on WiFi spread pretty evenly between the two APs. I seem to have no issues at all. I also have a dedicated 5Ghz network for streaming devices (mostly Chromecasts), and a third 2.4+5ghz network for phones and laptops. Overall, about 100 devices total.
My phones and PCs can easily pull 350+Mb/sec so there seems to be no noticeable congestion issues.
Client overhead can be reduced by disabling AP support for the old B protocol. Plus selecting short preamble. I have not seen B used in like 20 years so unless you have some antique wireless device B is not needed.
Looking at the specs for the Unifi AC Pro i am pretty sure that is a AC Wave 2 device.
Actually looking at the specs of that device it called out MU-MIMO or Multi-User MIMO. That is a goof on my part as that is what i was thinking of earlier. MU-MIMO allow for better simultaneous communication to multiple devices while MIMO simply allows a device to span multiple spatial streams to maximize bandwith.
MIMO came with most N decices over 150mbps speed. MU-MIMO may be on some AC wave one gear as a optional feature, but was required on AC Wave 2 onward. I am sure Wifi6 added even more features to improve bandwith.
