Realistically, at the basic training level, expect to be on PRes courses. The RegF runs the courses it needs for its people. PRes have somewhat different training standards in terms of what material must be covered versus what is considered supplemental. When you join the PRes, it should be clearly communicated to you what the expectations are regarding availability for that first summer.
Once you’re qualified in your trade, more opportunities may open up down the road. The PRes has recently been assigned unit level ‘misssion tasks’. Some units will get training in mortars; others in pioneer tasks (basically low level combat engineer stuff), some get heavy machine guns, some get basic reconnaissance patrolman courses. Other opportunities might include basic parachute, complex terrain, etc.
Where it can really open up is after you’re a qualified NCO. There are various instructor level courses (for instance I got Urban Operations Instructor) that are aimed primarily at the refs but that may take some reservists. All of those ‘mission tasks’ have higher level qualifiations as well where the reg/res line won’t mean much. And of course if you volunteer to deploy overseas there can be more as well as preparatory training.
For now, plan your life so as to get trained, and then work hard and don’t suck, and you should find some good opportunities in time.