I'm at 4.

What are the nuts-and-bolts reasons that would make 5 perform worse?

Each take about 10msec airtime (beacon+various broadcasts+probe responses+acks etc NOT including actual client data). (simplified)

Beacons repeat every 100msec. So you're already wasting up to 40/100 of airtime for management/misc frames

Wifi is a shared half duplex medium

Thanks!

Previously, I've never thought much about the airtime required for beacon transmission, nor that it increases as SSIDs are added.

Thinking about it now, I can see some ways to improve the cost of these SSIDs.

Like, increasing the minimum speed/excise old protocols (I probably don't need 1Mbps 802.11b at all in 2026 and can't think of any strictly 802.11b-only device that I've ever owned) to decrease the time that beacons use.

That seems like one obvious improvement that should be is free of other tradeoffs.

There's a few other things I can think of, but I'm not done thinking about it yet. :)