Hi!
First year cadet here. In terms of time management, I do find it time manageable so far, but keep in mind it does mean having to give up on some other things. Personally, I've found it a bit harder to make to uni or society events, cause they're either during work or in the evening and at that point you might be quite tired and you're just thinking, 'I just wanna go home'. I have a friend doing a cadetship at a different company from me and she has done much better than me in terms of engaging in that social aspect. One caveat for me in this regard is that I do have a one hour long commute, so it is a bit more effort for me.
In terms of just purely uni-work balance or effort, in one way, it'll depend on which company you end up working for. Remember that after the first interview with PCA, you can only go on to interview at one of the offering companies. Because of this, doing your best to find out what the company culture is like can be really important, and it was a big factor in why I chose my current company. UBS has been in this for a long time and they manage a lot of cadets, so they are a bit stricter in how you approach uni and work in terms of your study and workload, and the expectations for their work are a lot higher in terms of the hours. Luckily for me, my company is a lot more flexible and encourages us to take time off to study for exams and ensures we get the most out of uni too, and we don't have to work insane hours (yet, reporting season will probably be a different story).
In another sense of how much effort you're putting in to each, it'll also depend on what you're looking to get out of each. If you want to do relatively well compared to your uni cohort and be on the upper end of the class, then balancing that with work is very much possible! If you want to be university medal sort of level of achievement, it would be a lot harder to manage. Setting manageable expectations of yourself is going to be important in terms of your mental wellbeing and also managing other aspects of your life like social or physical health.
Ultimately, there will be some sacrifice needed in the end. For me, that has meant not really attending a lot of uni events or society events, but that's partly a consequence of me being 17 still and having to travel a lot. Still, your health, both physical and mental, should still be one of your top priorities, as well as doing well in uni, work and keeping your social life alive and thriving. It's a balancing act for sure, but 100% doable, and it can be incredibly rewarding.
Also for the tech or business question, apply for both? I'm honestly not too sure cause the tech ones haven't been offered in ages.
Hope that helps!