The model that I used was kerosene version that required an electrical outlet.
You will definitely want to purchase two add-ons if not already built in to this model.
1) automatic thermostat to shut if on/off at a set temperature
2) CO monitor to shut if off when CO levels rise
If you are thinking about using this as an unattended heater, that would not be advisable unless you have some kind of fresh air intake and exhaust, I certain that the manufacturer would advise not to leave this unattended.
For the most part they work well to take the edge off low temps but, they tend to direct heat in a specific direction lacking ductwork to evenly distribute the heat.
We don't know what climate you live in or the reason you want to heat the garage. Most garages are poorly insulated and have cheep windows and those huge doors that are not that great at insulation. The other problem is thermal mass around here. The floor is a huge mass that if you go out there in zero weather to work it would take a couple days to adjust to the new temp. The best type heat is something like you show or a torpedo heater as mentioned above but they have to be watched and you have to be careful about combustibles as well as co2. My garage I set up with two rooms the main big area and a small heated and insulated work shop about 12x12. I don't heat it all winter but it only takes about 30 minutes to be nice and warm. If I'm working on a car I can go in grab warm tools and warm up a little between working.
I don't know about the brand you are looking at but they are made to heat you and the air and not really the building long term. Just be careful.