unique A/C system set up

I have a 1960s 5 bed/3 bath two story house where I have converted the garage into a master bedroom. I have a Mr. Cool 1Ton mini-split in that bedroom conversion that is compatible with your puck. The rest of the house is cooled with a down flow Carrier central system from the second floor between the trusses with a Ecobee4 and sensors for control. I have standard 4X10 floor vents up stairs and 8" round diffusers in the ceiling down stairs. So my questions for your system......

1) If I get a puck to tie my mini-split to my central A/C via the Ecobee4, can that same puck also control the smart pucks for the central A/C?

2) Do you have a solution for my down stairs round diffusers or will in need to build new rectangle boxes?