First of all, I don't rely on Apple's proprietary apps (Music, TV, Photos) to store / use the appropriate files - precisely so that I can back them up to whatever media source I like.
As noted by Andrey84, you don't have a lot to store, so I wouldn't be too worried about the footprint on your new Air, but always worth backing up to outside sources, too. There's plenty of cloud storage options - a couple noted above - but as always with that, you're relying on the vagaries of the internet and the company involved. Even a temporary problem with either of those, and you may lose access to your files for a time. Or a company changes the storage / cost on you.
While I use some online storage options, for the most part I do backups to local sources. For example, I have a portable SSD set up as my Time Machine, and another set up as simply a Backup (Documents, Movies, Music, Pictures, Software Install Files). I also - once a month - refresh backups on a USB drive I have. And certainly your 30GB (and growing) files could easily live on most of those for very little financial outlay.