I did gcse art, and it is a lot of work! to do well you need to be motivated from the start. However, it is a fun subject if you enjoy art, and if you are already doing well it will suit you. I definitely think you should take it on if you want to do architecture, it will really develop your skills. Dont let other people put you off, it is a really good subject and a great creativity outlet for the stress of gcse exams. It is only a bad subject if you let the work pile up.
glad I could be of some help! personally, I wrote out a big list of what work I knew needed to be submitted, or completed by the end of term and then I could cross it out as I finished it. Also, it helps if you know exactly what your coursework should look like, so I'd recommend looking up other people's on youtube etc. If you have a day where you have a lighter workload, try designate a few hours to work on it then. Do not do your work the night before it is due (you probably already knew that though.) If your school offers any lunch or after school art clubs, try to attend them - art teachers will be able to help you and being in an art space really helps to motivate. Finally, for every piece of art you do, note how long it took you, what mediums you used, what was the inspiration (for example a particular art style) and what you like and dislike about it. Most exam boards want to see that sort of thing, so I'd strongly advise doing it from the start. Sorry if that was a bit of a ramble, all the best to you