you would be very comfortable with warm floors.

Hydronic heating is hot water heating. You want radiant heat in the floors, either hydronic or electric?

What is your current heating fuel source, nat. gas, fuel oil, propane, coal? If you are contemplating taking some of your home off of gas and switching to electric heat, it will cost you in the long run. That is clear. With the other alternatives, you have to do some calculations.

Radiant, in floor heat will work and makes sense with an hydronic system already in the house. You will be taking advantage of the fact that you have a boiler that is already rated to heat the house (or so we hope). if it is designed properly, It will be warm enough if it was warm enough before the renovation, maybe even if it was not warm enough before the renovation.

With in-floor heat over unheated spaces, you have to pay attention to what kind of material you install over the pipes. It can not be damaged by the heat and it must not be significantly insulating. You must have excellent insulation between the pipes and the unheated space underneath.

Kick space heaters, and other heat exchangers can work as well. Be aware that they will make some noise. Some are noisier than others. Be sure that they are installed so they can be serviced or replaced. Nothing that is mechanical lasts forever.

I don't understand why choices are being so restricted. Why no mats over the garage? Why no combination of toe kick heaters with radiant hydronic floor? For that latter combo, the toe kick heaters will need to be relatively large because the water temp will be lower with the radiant, in-floor hydronic if they are on the same zone.