Personally, I`d simply use a burning App/Program & just CDR`s, a reasonable branded disc will cost approx < £10 for 100 CDs, ie < 10p per CD, cheap as chips.
Simply drag & drop the data to the Burning app & burn, no chance of deleting the data, as stated always burn 2 copies if its "Mission Critical".
I think what you are referring to with regards to CD-RWs is Packet burning software, whereby you Overwrite/Re-Write the data, in a similar way to a Floppy...I don`t trust this stuff & prefer to burn a copy that can`t be altered.... Yes its wasteful, not environmentally friendly, but it does work.
For anything really important, make sure you have 3 copies & store them in different places.
I try & cover every base, I use External HDDs, Internal HDDs & another PC with pretty much copies of all things Important, anything seriously important will also go onto CD/DVD...