What IB subjects should I take?

Hi! I'm an IB year 2 student so I hope I can answer your questions! I think that the two main things you need to consider when choosing your subjects are: which subjects you like/are good at and also (maybe a bit more important) what subjects you need for university. Most students at my school who want to do architecture are taking art (Visual Arts) and some are taking Maths HL or physics (but it depends on their chosen unis). If you are struggling to choose a third HL subject and your uni has no requirements for the third HL, then maybe you should pick a relatively "easy" subject like English B or social anthropology or psychology (if your school offers them). I'm not saying that these subjects are a walk in the park but I've heard that the workload and assessment components (e.g. the papers you need to study for the exams and the Internal Assessment) are better than in other HL subjects. A lot of my friends are taking Visual Arts HL and they say it's by far their most demanding subject. They tend to focus a lot on it and spend all night (even pulling multiple all-nighters to finish assignments). I'm not saying that to scare you off, just to suggest that maybe an easier third HL might allow you to focus on your art.
Now for Biology HL...it's honestly one of my favorite subjects but the workload and material you need to learn is a LOT. I'm afraid I don't know about A level bio so I can't help you there, but bio HL is definitely a commitment especially with lab work. Two of my bio classmates took bio HL without Chemistry HL or a science background in general and they really struggled with some of the extra chapters that bio HL has compared to bio SL, so maybe that's something you can consider by looking at the IB Biology HL syllabus.
For languages I'm taking English A lang and lit HL and modern greek A lit (our school forces us too, don't know why). You might know this already but there are two language groups you can choose from Language A (native speakers level) and Language B (second language, less prior experience). In Language B, there is also a thing called language ab initio, meaning a language you have no prior experience with. For example, that could be Spanish SL ab initio (IB only offers ab initio at SL). Language B subjects are considerably easier and less time consuming than Language A subjects. They have less things to do throughout the year and less assessment components (for example for English I have two externally assessed projects and two oral exams, while in English B my friends have only one of each). I don't know if you can take two language B subjects but if you can then maybe you could choose French B and/or Spanish ab initio if you feel that you're going to struggled with languages (and of course if your uni has no special language requirements). Overall, I would say that if you don't need a language A or a language A at HL (I still regret that decision), maybe choose language B or ab initio.

Wow that is long, sorry! But I hope I answered some of your questions, feel free to ask more!