Optimised apps were (not sure about now) ones that used SSE, SSE2 etc to make the benchmarks higher to claim more credit.
Back when I BOINC'd, they were needed for the linux client because for some reason, the linux client apppears to be penalised and got lower benchmarks than the exact same PC on windows.
Nowadays there's not really needed as the BOINC client itself uses SSE IIRC.
TBH I doubt you'd see a huge, if noticable increase in points stripping them all down to the bare essentials.