Never mesh if you can avoid it. Mesh halves your bandwidth and doubles your latency - at least. Especially with pro-sumer gear like ubiquiti.
If you *have* to mesh (and you don't), remember that you never place your "repeater" in the room you're in. If the signal is poor, then the signal to your repeater will be poor, and all you'll have is the false sense of satisfaction of full-bars with the same weak signal. Place your repeater about half way (bias toward the root access point) between where your root AP is and where you need more signal.
For the love of God - it's 2022. Use the SAME SSID AND KEY FOR ALL ACCESS POINTS. Never have multiple SSIDs or the same SSID and different keys. Your APs should be smart enough to listen before they lock on to a channel, and roaming for the closest AP is up to the *client* device. Again, ALL THE SAME...