My turn to chime in:
1. Your first real decision is "Officer or NCO?"
If the answer is "Officer", then a university education is essential. There's more than one way to do it, but getting that education is a core part of your career progression - and you will need the study skills, even if you go Infantry.
On the NCO side, I don't think a university education is a "must have" but I do think it is a "nice to have" - but I'm rapidly exiting my lane here; you'd be better off discussing this with NCOs than me.
2. If you decide you want to be an officer, then attending RMC is a very good thing. It's not essential (and for that matter, it isn't a guarantee that you'll be a good officer either) but it does lay a good solid foundation for a life in uniform.
Grades matter for getting onto RMC, but so do a lot of other things. Don't take yourself out of the running - apply, and see what happens.
Part of the RMC acceptance process is that not everybody who is offered a position accepts it. There is a "B List" that they fall back on to fill slots rejected by "A Listers". It is possible to squeak in at the last second this way, and more than a few "B List" types have gone on to become successful officers.
3. DO NOT allow yourself to be swayed by pension, retirement, or civvie skills arguments. They are utterly unimportant when compared to the quality of life that comes from doing what you love.
Put your helmets on, war story time:
Back when I was going to CMR in the late 80's/early 90's, I got in as a pilot and as a Computer Scientist. While I was there, I discovered the Military and Strategic Studies programme, and I also discovered that I had some small amount of talent as a field leader. The pilot thing was nowhere near as much fun as I had expected, and calculus sucked golf balls through garden hose. What I WANTED to do - and very badly - was to switch my degree over to MilStud, and my MOC over to Armoured.
My buddies, who were all pilots, talked me out of this no less than three times. Each time, the argument was "what are you going to do when your stint is up?" - the idea being that you get the CF to pay for your science or engineering degree, you fly transports for 5 years to get hours and multi-engine certification, and then go fly for Air Canada making the big bucks. The unstated assumption here is that a Armoured officer with a MilStud degree was worthless out on civvie street.
The end result was that I wound up doing things I just wasn't all that interested in doing. It made my life drudgery, and the quality of work coming out of an unhappy drone just isn't very high....
Half a lifetime later, I managed to rectify the problem, and became an Armoured officer, and my quality of life skyrocketed.
I have very, very few real regrets in life, but the biggest is that I didn't remuster to Armour and change my degree to MilStud the first opportunity I had, and that I had told my entirely well-intentioned buddies to go piss up a rope.
It is far, far more important to do what you LOVE, rather than doing what you think (or what someone else thinks) is "smart". If you can make your career in something you love doing, then all the incidentals take care of themselves.
DG