Could P2SH be quantum safe? As it is NOT based on public keys, which are weak with QC.
Not, this is not quantum safe the same as P2PKH. Because it based on public keys, you provide them in your scriptsig of redeem script.
1. Maximum Bitcoin script is 40000 weight (or 10000 bytes before SegWit activiation)
If i remember right, P2SH redeem script is just 520 byte of space.