Hello all! I am new to MESH networking, and have a couple of questions...

1. I have a 3-Node Deco M5 MESH system! 
   • Mostly it works fine... even with ~30 devices (some are light switches and other low action devices). I do NOT "usually" lose Internet, and those I have experences, I can mostly chalk up to our ISP. 
   • Coverage is usually good, EXCEPT that I have the same problem as others have posted: In some cases, my iPhone or Laptop will insist on grabbing M5 Node first acquired, even if I am closer to another node AND that node has almost nothing on it! I cannot tell if the device picks up and HOLDS the connection, OR if there is a setting I am missing somewhere to make this work right! 
   • Example: 
     • Last night, my daughter started a WhatsApp call when she was in the Kitchen (Salve M5 node there). She went upstairs to her Bedroom (another Slave M5 node about 15 feet away), but her call stayed on the node downstairs. Twice and far and through the floors.
     • When she told me she dropped back to Cellular because the WiFi signal was so bad, I looked and MOST of the house was connecting  the Kitchen Node! Including my iPad, which had been "off", and I was holding in the bedroom right next to the other slave node! 
     • My solution: I rebooted the Slave node in the Kitchen, all the devices scattered around and found a new connection (my daughter and my iPad connected properly to the bedroom), and from there things were OK.
   • I DO have "Fast Roaming" switched ON... and he oldest device on the network is my daughter's laptop (2016). Our phones are all from 2018, other laptops are 2017 and 2018.
2. So now I need advice on some Options:
   1. Should I switch OFF Fast Roaming? But I thought that seamless movement was the whole purpose of MESH?
   2. Should I get another M5 Node to spread things out even more? Our home is ~3000 sq ft, but part of that is a finished basement... and the M5 is supposed to cover a larger area.
   3. Should I add a WiFi Extender in Critical Areas, like my daughter's bedroom (the farthest point from any node)? But even with the TP-Link R220 extender (leftover from before MESH), I believe my daughter will lose some speed... and for her streaming videos all the time, too much caching will bring too many complaints.
   4. Other ideas? 

Thanks for reading... any advice or ideas are very welcome! 

- eli04