Maths and Physics degree transistion, career advice, suggestions. Which is it harder to transtition, making undergraduate in maths and master on physics or making undergraduate on physics and master on maths?

DISCLAIMER: I am not from USA or any english speaking country, so my english may be terrible, in my daily life I never use it and I learnt it through use. So sorry for any grammar mistake or misspell.

I am curious about how hard is the transition between those degrees Maths and Physics.

An old engineer that is close to me told me that the best is making these degrees for reaching good levels of abstraction so it helps you think outside the box. And then a Master in Mechanical.

My best friend told me about based in what she knows about me about doing Biomedical Engineering, and studying (by myself or minor/alternative degree) separately maths and physics.

My father thinks that I would enjoy more Physics .

A great teacher of highschool thinks that the best would be Maths.

So I am looking about the prospects of each path. So I will can make a more informed choice about what to study. Which is it harder to transtition, making undergraduate in maths and master on physics or making undergraduate on physics and master on maths?

Thanks for your time