Hi!
Even though it might feel a bit early to think about all this, I’d definitely encourage you to start considering what you’d like to study at A-level and possibly at university too. For example, it’s quite rare to be able to take Computer Science at A-level without having done it at GCSE first. And since most universities require A-level Computer Science to apply for the degree, it could limit your options later on.
That said, you mentioned you’re passionate about art. From what I know, many universities will accept a portfolio if you haven’t taken Art at A-level, but that means you’d need to work on your skills and build up that portfolio independently in your own time.
As for the Spanish prediction—unless you already speak it at home, I’m not sure how a teacher could confidently predict a Grade 9 two years in advance! But if they are right, that’s only a good thing. A strong set of GCSEs can be a big advantage, especially since many competitive universities look at your GCSE results as well as your predicted A-level grades. You also mentioned you don't think you'll enjoy it which in itself could impact the amount of effort you put into studying and actually getting that grade 9.
I would personally recommend swapping out RS with Art as there isn't much point in taking it unless you really enjoy the lessons and keeping Spanish if you're confident in your teachers prediction. However, having said that I think its important to give your future self the most options possible (all of this is coming from a year 12 student).