I went through enlisted pipeline in 2001 (age 24) and officer side in 2005. Obviously the enlisted side was more restrictive than the officer side given most of the enlisted students are straight out of high school or college dropouts (like me). One note, though: if you are married (like I was) you don't have the same limits. You still have the same uniform limitations, but that's about it.
One bonus to being married at boot camp... your paycheck is much larger than everyone else's bc you are getting BAH, not to mention you get E3 pay while most non-nukes get E1 or E2 pay.
A note on nuke school... it isn't in "Charleston". It is in Goose Creek... the buttcrack of Charleston as my wife calls it.
A note on career progression... if you have a desire to make it a career, put in an STA-21 app while you are at NNPTC. You should be able to put in your app while in power school. If your recruiter hasn't told you about it Google it. It is one of the best deals in the Navy. You get your regular pay plus they send you back to college to get your commission. I when through the program and it was awesome.
All in all you'll serve yourself well to be in shape before you go to boot camp, but it all depends on the attitude of your RDCs. Mine had short timers but there were some that loved to break their recruits. Being physically fit will put you on top of your peers. Nukes usually get tapped for leadership positions within their boot camp division, so look up the chain of command of a boot camp division before you get there and mention to your RDC what you want to do... if there is anything.
Good luck and have fun!! By the way... highly recommend EM for a rate. It was my first choice and I got it. I'm sure anyone here can tell you the differences.