[hayden55]

Registers and dampers aren't the same thing so hopefully you know i mean adjusting the dampers on the main legs attached to your central air unit's body. It has these wafers like a throttle body that adjust air. Adjusting registers is the last thing you do as they aren't a great way or efficient way to reduce air flow but helpful at the end after adjusting the whole leg if certain rooms need more or less cfm.

The variable speed blower would be interesting for when the unit isn't heating or cooling but when it is you want to go back to default cfm or your efficiency will take a hit and more than likely your furnace will just overheat and go into thermal protection mode in the winter. The mini splits with an inverter can run at variable capacity so they can match the fan speed and be just fine (i wish we could do that though lol)

Govee has some wireless temp/humdity sensors on amazon. Just as accurate on both as the expensive ones. You can connect 10 on wifi and they datalog every hour. If you can put them all at the same height and away from registers so you get a good measurement on room temps it seems like it would make measuring a lot easier.

Yup so the mini splits have a coefficient of performance while the resistance heaters and natural gas heaters have efficiency.
NG furnaces with a metal exhaust pipe : 78% efficient
NG furnaces with pvc exhaust : 82%+
electric resistive: 33%
Air source heat pumps: cop based on temps and delta T
But basically they use 1 unit of energy to do 3 units of work. So they can be a lot more than 3x more efficient.
So they might have a cop on average of 2.5 in the winter and 4 in the summer, so lets say 325% efficient on average.
The big thing to worry about though is cop is variable with temp so it comes into play when you lose heat because its too cold outside. Some work down to -5 or -20 or -40 depending on unit and thats a massive delta T to a 70 degree inside temp in the winter and they will basically have a cop of like 1 in those conditions so you will need back up heat for those 4 days of the year we get winter storms. Still personally looking into a central air handler mini split unit that will get me the performance i need with my natural gas fire place as a backup.
But in recent years they are finally getting more efficient and usable. A mitsubishi central 3 ton unit has a seer rating of 19, but the new itty bitty 6k unit they just came out with has a seer rating of 33. So it looks like the 33 seer unit has a peak cop of 9.7 which is insane.
The only issue with the ductless units is they suck at removing humidity from the air so i personally would stay ducted.