PNP and NPN transistor characteristics for this project (see link inside for schematic)
S8050 and S8550 are "obscure" transistors in my opinion, why use those?

They will probably just work though, their Hfe is > 100 and usually that's all that matters in such a low power circuit.

But looking at the schematic (of which you should include the picture, not just a link) I think almost any general purpose NPN/PNP will work.

I'd use BC547(NPN) and BC557(PNP) but that's because I have plenty of them (as do many other hobbyists). If you're in US you might choose 2N3905(NPN) and 2N3906(PNP) instead.

But really: it does not matter much, the circuit does not rely on "special properties" of specific transistors.