If you want plug-and-play reliability across floors the FHSS non‑WiFi sets tend to beat app cams; the Infant Optics DXR‑8 Pro or Eufy SpaceView have been solid for us through two levels. If you stay with WiFi, put the router centrally, create a 2.4‑only SSID for the monitor, and lock the channel to the least congested of 1/6/11. Audio‑only DECT units like the VTech DM221 or Philips Avent are even more bulletproof if video isn’t essential.
Most boards feel best at the high end so 14 to 15 for flat water and bigger riders and 12 to 13 if you prefer softer. Verify your pump once against any accurate gauge with a SUP adapter then use that offset forever. Temperature swings change PSI so check again after launch.