If I wanted to send another musician something I’m working on, would I need to send the VSTs and samples I used as well as the Renoise song file?
The samples are saved within the *.rns file.
The VST’s used in the song do also need to be send also.
cheers 
You will still be able to edit, the patterns stay the same, you only get an error message, no crash even… 
You can alternatively add a different sample/vsti in the empty instrument slot to replace the missing vsti.
if the samples are loaded by the VSTi (for example: you use a VSTi sampler such as Kontakt or HAlion), you have to send them separately, because they are not been saved together into the RNS file