Reg force you're looking at 7-330 ish timings. I'd imagine it wouldn't be the best for college classes. You could always go reserve, part time you'll only be working thursdays, and a weekend every second week.
Reg force you can be posted anywheres, chances are you will not stay at your place of entry.
Reserves you will work at the nearest reserve unit.
Most army trades will be eating up the same amount of time. Different trades will lead to different lengths of time for training. Anything army you'll be required to do a lot of the same basic courses like your BMQ & SQ.
If your highschool courses were up to par, you could always enroll to become an officer, be paid to go to university & choose a few of the courses in which you actually take. You go in normal clothing and are just another normal civilian in uni, but are paid to be there.
If going reserves for a part time job, imo either infantry or vehicle tech. Infantry will get you in shape, veh tech will increase tool knowledge.
Reg force? Do yourself a favor & go airforce in a spec pay trade. After 5 years in an airforce spec pay trade I am making as much money as a sergeant in the army who had been in 20 years. Give that some thought.
EDIT: Did not see your age. Read about the reserves, be smart and apply NOW, after two years you'll receive your corporals. Then apply for reg force, your corporals will transfer over and you'll be laughing as you're starting off at like 15k more a year than the other 18-19 year-old's applying.
Cheers.