As an ex-staff sergeant who was in 6+ years including time spent in Afghanistan, I can tell you that there are many "truths" to enlisting, and a little bit of every rumor you hear is true. The most important things to remember are: until you swear your oath and sign on the dotted line, they cannot force you to do anything. Don't let a recruiter or anyone at MEPS tell you "you have to take this job". Recruiters play up jobs like security forces and services because they are easy to test into. I would shoot for scoring well on the ASVAB, and also ask to take the DLAB so you have the option of maybe going to language school. If your ASVAB scores aren't high enough, look at the jobs you qualify for and ask yourself this: what skills will I learn in this job that I can use on the outside? Will this job afford me time to utilize my tuition assistance? If I could do one thing over, it would be getting my degree before I got out. Luckily, I worked in intel, and based on my skillset I was able to get a job that pays well without the degree - but that's only because my job afforded me opportunities to learn valuable skills and also to get a clearance. However, if I had a degree, more options would be open, because that is pretty much just a checkbox now. Your degree could be in underwater basket weaving, but as long as you have work experience and skills, employers don't care.
As far as bodybuilding friendly jobs, ALL jobs are bodybuilding friendly in the military. You get free gym access (and military gyms range from hardcore, to crossfit, to really nice and clean commercial-style facilities) and an allowance for food. There ain't much more you could ask for than that.
Every job in the military is necessary and dignified, as is all human labor, and as such deserves respect. But in the outside world, profits and marketing rule, so I'll leave you with this: during my transition class while I was separating, I sat next to a Navy Petty Officer who had spent his time in as a cook on a submarine. A hard job that not many people would be willing to do, and I respect the hell out of the guy for it. But when we were doing an exercise where we were supposed to brain storm resume ideas regarding what skills we learned in the military that could apply to civilian employment, his sheet of paper was almost blank.