Channel planning
Two access points on the same channel do not add capacity — they take turns.
How do I fix co-channel interference?

Run the channel optimiser: it assigns channels across the floor to minimise overlap, and reports the improvement. Verify on the Channel Interference layer, where red means two access points on the same channel are within earshot of each other.
Why does adding power make interference worse?
Raising transmit power extends the cell, so more access points on the same channel can hear each other and more time is spent waiting. Interference is solved by the channel plan and by cell sizing, not by power.
Common questions
Which bands does WiFi Weave model?
The heatmap models 2.4 GHz, 5 GHz and 6 GHz, plus 3.5 GHz (CBRS band 48) for private cellular. Path loss, wall attenuation and the frequency term all change with band.