Hallo
I'll chime in for bio SSP!
Bio SSP is great and I found it not much of a step from doing Adv level bio, and it's an absolutely fantastic course. The only difference is you get to do way more independent and higher thinking lab work. They'll expect you to pick up practical techniques faster(like you'll be soaring through learning new equipment) The theory content is the same.
I only did Adv Chem, so the person to speak to regarding that is someth1ng. But SSP chem again, does the same theory lectures/tutes as Adv kids, but escapes the annoying first year chem labs that then the fundies/std/pharmacy/adv are cattle called into together (which has no relevance at all to what you learn in adv chem). So I'm going with a similar vibe to say it's like SSP bio where you just get to do much, much better pracwork (though adv bio pracs are way better than chem pracs cause they are actually relevant)
If you are a smart cookie, I know some people in my year did two SSPs at a time, or a mixture of TSP/SSP and managed. I think someone even did Chem/Phys/Bio SSP in same sem, the gun.