Need recommendations on system

Hello all.   I was looking for some ideas for a system using flair pucks and either an ecobee thermostat or nest.  I'll give my current setup and if you have ideas on how these would work together please post.   I currently have a 4 zone mini split system with no Wifi so pucks would be needed to control each of the 4 heads.  My other system is a Rinnai direct vent heater that can heat the whole house (it's under 1K sq ft.) which is wired to a wall thermostat on a schedule.  I plan on using the Rinnai for the coldest months and the rest of the time use the mini split.  Or just use the mini splits as a displacement type setup for the colder months with the Rinnai.  I'm just not sure on how a smart thermostat and flair integrate together for this type of setup other than individual controls of each system in the same interface?  For example, am I using the Flair app to control the home or the Ecobee or Nest?  Or using them all individually?  Any help and ideas would be appreciated.   I do know if I'm on the Rinnai alone I feel I would need a temp sensor in the bedroom if using Ecobee just to get the system to average a little more to bring that room up 1-2 degrees.  Also the main living room that has the heater always has that mini split head running more than any other room and I think it's in part to the stairs to the second floor are in that room and a lot of the heat travels up there.