Reading the FRI paper and just learned that Zcash was built using
QSPs - are there any other modern-dayish protocols that use QSP for representing NP statements? I thought only QAPs were used in practice and that the benchmarks (from either GGPR13 or groth16 I forget) heavily favor QAPs

Ah, so maybe the Zerocash paper used QSPs because they were more popular at the time before Zcash swapped them out!

applied crypto, security, experimental things. head of research @__geometry__, puzzler @__zkhack__, producing blocks @zkvalidator, cryptography @cLabs