Guard / Reserve is an excellent path to a professional flying career, allowing you to serve a good cause, get paid, learn a lot, and have your flight training provided.

Joining an active duty service branch is a major time commitment (ten years) and I would only recommend that if you think you might be interested in an active-duty military career, with more staff/ground jobs than flying.

You will need a degree to be considered for ANG/USAFR pilot slots. You could get into the army guard as a helo pilot without completing the degree, but joining a fixed-wing unit would be the best bet if you're interested in airlines.

You could also enlist in a guard/reserve unit if you wanted to get started now, and then hope to pick up a flight slot as an internal hire (assuming you do a good job as enlisted, better odds than off-the-street applicants). This would involve at least some number of months for training, which would delay your civilian flight training.