GCSE French is a tough one to talk about. For my course, 60% of it was coursework, through 2 speaking assessments and 2 writing assessments, and then 40% was exam through 1 reading exam and 1 listening exam.
The coursework is a ton of work. It takes so long to do, and so long to learn off by heart, and it's so easy to mess up on the day when you have to actually do it... but if you really do put the effort in, it's honestly the best thing ever as it means you have 60% of your course as a high grade. I managed to get an A in my 60% coursework, so I had that to boost me up for the real exams.
The exams, if I'm honest, are mostly just making educated guesses; you'll probably never be 100% sure on the answers, but a lot of the time it's relatively easy to guess and get them right. In my two exams, I got a B in reading and a D in listening (I was very close to C), so I got a B overall in French. Overall, it's a hard GCSE, but if you put the work in, it's not impossible to get a good grade. I'd assume Spanish is very similar, but most probably a bit easier as people do Spanish for less time than French over their school-years.
As for Economics GCSE, I never did it (I'm still struggling at AS-Level Economics as a result of it), but I'd assume there's isn't too much maths; I believe it is mostly learning terms, and learning graphs. If you're able to do Maths GCSE, then you'll have absolutely no problem with it whatsoever (it'd be much easier).
Sorry if some of the things I'm saying don't make much sense, I'm a bit tired haha