Moresampler is not an ideal resampler for scream voicebanks, as the u flag only plays samples straight through and does nothing to the length. If you use tn_fnds, you can set the flag W to -1 and it will disable pitch shifting while still extending note lengths.
However, Moresampler is still a very useful general purpose resampler for other singing voicebanks.
The most essential plugin to have is iroiro, downloadable here:
https://ux.getuploader.com/bizz_v/download/181
It combines several basic utilities into one plugin. Any other plugins you download will depend on your workflow and needs.