If you heat your garage the relative humidity will automatically drop as a result of heating the air, no matter how you heat it, so you shouldn't need a dehumidifier during the winter. An un-vented flame type heater (propane, kerosene, etc.) WILL add moisture to the air, however. The combination of heat and lower humidity will help bikes and clothing melt and dry faster. A fan to move the air over the objects will also speed things up and properly aimed will help keep the warm air from collecting at the ceiling where it does little good.

I'd dry shoes and gloves in a heated area, though. If you are using a radiant heater place it where it will direct heat onto the objects to be dried; stuff in the shadows will stay relatively cold. Any type of electric heater will have similar efficiency as all of the electricity will be converted to heat; a radiant type of heater will tend to warm the objects it shines on more that the air although the warm objects will indirectly heat the air. 1500 watts (or so) of electricity will eventually have the same heating effect no matter how you deliver it.

I have a closed-cell mat in front of my workbench, more for foot comfort than for warmth since my basement shop is heated, but not standing on cold floors will help keep you warm while you work; there are also heated mats available. .