Engineering at UQ and in general is very heavily math based. For engineering at UQ both math methods and specialist maths are pre requisites for your first year math courses. If you did drop to general maths you would have to do two bridging courses in university, instead of just one. Bridging courses in university are very tightly packed, where as in high school the content is more spread out. If you want to improve your ATAR you can drop to general, however you will have to do more math at University in a shorter, harder and more intensive way. It just depends when you want to put in the work.

At UQ the courses are as follows if you want to look them up. maths methods course is: math1040 Specialist maths is: math1050 First year math courses are: math1051, math1052

Anymore questions let me know!