are these good options? Watch
Bio is going to be a memory test for a lot of it; but also is going to include more statistics type Maths than Physics and Chem. Its got a lot of content.
All the sciences are quite hard same as Maths. So don't expect hard work to simply equal grades like in GCSE, you might fail a couple times before you finally master a difficult part.
STEM A Levels IMO are trickier than Humanity A Levels. So what I would recommend is picking your two favorite STEMs plus one Humanity. People might claim that there's some overlap between the Sciences and the Maths. But that's only really FM and Maths. I found Physics, Chem, Bio curriculum was almost designed so there would not be that much overlap.
If you want to game theory it, pick a humanity with few exams to do, and more course work. This will reduce the amount of exams you have at the end of year 13, free your time to focus your efforts or even do a resit from year 12 to maximize your UMS.
History is quite good even if you didn't do it for GCSE and your essays skills aren't the best.
Difficulty IMO+friends opinions and shown in our results: (most to least)
For degrees: (No order)
Maths + Physics or Further Maths for Engineer even for Biomedical it's all you really need.
Chem + Maths for Chemical Engineer tho. (Physics is a bonus for both)
Chem(always required) + Bio or Maths some even require both for Medicine. (Aston for instance considers Physics as well required RIP, but not places like Cambridge who only want Chem + Bio or Maths or Physics)
Maths + FM for Maths degree.
Physics + Maths for Physics degree. (Chem is a bonus)
History + anything really for History same for Psychology and a lot of humanities.
For prospects generally: (By highest salary to lowest)
Engineer (Chemical Engineer being highest because of petroleum, but subject to change to things like Aerospace)
But remember it's completely up to you and what you want to do in future should be the most important factor to concern yourself with.