I have run my brothers sub-floor suspended tube for nearly 20 years at 180°F supply from a Buderus 124 propane. The southern yellow pine 4" plank floor is still perfect 100 years and counting.

A propane condensing boiler it is. All condensing boiler have ODR and yours should make DHW as well. This is the combination I installed with my first radiant floor heating system in the mountains west of Denver circa. 1987.

Get a proper heat load from an experienced designer. Over-sized, poorly controlled boilers burn more fuel, give less comfort and don't last as long as they should. You want to choose a boiler that is well supported in your particular area.