I'm contemplating either the Amazon or iTunes music backups ..., everything else can go on flash or one of my portable HDs and into my safety deposit box at the bank.
iTunes is cheap ($25/yr) but limited to 25K songs and any matched tune is kept at their 256K AAC format. Amazon (also $25/yr) will keep up to 250K songs, but I couldn't find in a quick search the bit rate (I assume 330K as that is their standard MP3 format, but not sure).
Dropbox, Google Drive, One Drive on a regular basis all for different reasons.
Dropbox is my favorite
3 externals, 3 computers for local backup of all other important info.
2 of my externals are off site.
Allwaysync is my friend. Buy the pro edition and fall in love.