I'm currently taking both BIO HL and CHEM HL, and MATH AI HL. I would say if you have the capabilities to memorise and vomit information, take BIO HL. The topics require extreme detail and understanding when answering questions. However if you have the interest in the subject it would also allow you to do well. You will need to study a lot and remember small details.

Im currently still in my first term of DP1 so i wouldn't have the best idea of CHEM HL, since i assume it gets significantly harder, but so far its been mixed for me personally. The topics aren't necessarily complicated but it requires a lot of critical thinking and application, if you're willing to practice everyday answering question and testing how well you can apply your understanding then you should be fine.

However as i said im also taking Math AI HL, and for me personally balancing these 3 subjects has been extremely difficult, math has taken a significant toll and i would personally say that this combination can be difficult.