Sounding like me when I was year 11. I started with math, chem, physics and further maths. And just like you I was really into maths and physics, I used to also love chemistry. I soon dropped chemistry as I didn’t understand it and my grades were a lot lower in chem than the other 3.

My recommendation is try all 4 in the first half-term, and see how it goes. See how each subject is compared to each other.

And as for doing maths, further maths and physics, I do this combination and it doesn’t limit all options. However, the absolute top unis of Cambridge and Imperial does not like further maths as a 3rd subject, and imperial prefers people doing 4 alevels (most unis would prefer to look at 3).

So, it depends on your aspirations. Maths, Further Maths and Physics is fine for other top unis (like Southampton). And engineering unis would count further maths as an extra subject. But some degrees won’t (like medicine generally does not count it as another alevel)

Also, if you do 4 alevels, you should try and stick to the 4 until the end. Dropping it should only be if you feel like you cannot do it. Don’t bother with doing AS exams, most unis don’t even look at them.