Engineering math is significantly more different: it's a lot of mathematical modelling which involves vector calculus and solving differential equations, which you don't even touch in high school.

Most of the topics you do in high school are pretty useless in uni. When they teach you a topic in high school, they go all out on it. E.g. complex numbers, you do all this stuff like complex roots and they go out of their way to make you do all these convoluted problems. In uni they don't care about this - all you need to know is what a complex number is and how to manipulate them. Once that's done (which will take about 2 lectures), they move onto more important things.

I wouldn't really compare high school math with uni. In high school math, you're given all the time in the world to master a particular topic by more or less doing all the problems in the textbook. In uni they'll smash through the content like there's no tomorrow and give you 5-10 tute problems per topic to practice on.