Warwick maths v Cambridge bio natsci

I’ve received offers for both and have already achieved the grades (4A* in bio,chem,maths,further maths) as I’m on a gap year so just need to decide which to confirm.
I’m wanting to go into a high paying career most likely in finance and really enjoy maths - I’m worried the natsci course won’t be enough maths for me and have looked and seen the maths option in part IB and then leading on to astrophysics in part II which interests me. Unfortunately I didn’t taken Alevel physics and although it says part II astrophysics has no requirements but recommends maths and physics in part IB, would I even be considered for that? Will I struggle a lot doing astrophysics with my last studying of physics being gcse or mechanics in my Alevels?
If I can’t go down that route and end up with a natsci bachelors in a biological subject eg pharmacology, is that much less competitive that Warwick maths for top finance jobs?
Also would it be possible for me to swap to chem eng after first year of natsci? I know that used to be how the chem eng course ran but has recently changed.
Apologies for all those questions :s