I don't think the jump is as big as people make it out to be.

Graphs look at how you can sketch without the use of calculus.

Complex Numbers is just an extension of algebra. It opens a wider set of numbers to explore and deal with.

Conics is an extension of the parabola/parametrics.

Integration introduces maybe 3 new concepts (IBP, Reduction, Partial Fractions)

Volumes is an extension of Integration and Volumes in MX1 - looks at 3 new concepts (shells, slices, volumes of solids, e.g. prisms)

Mechanics is an extension of physical applications of calculus.

Polynomials is an extension of polynomials in MX1.

Harder 3U are the higher order MX1 questions in probability, circles, linear algebra etc.

There's actually quite a lot of overlap, whilst being introduced to new concepts. And what I've noticed is that doing MX2 makes MX1 feel quite easy.