Best way to store files remotely?

Try Mega 50Gb free. You can select what to sync with the local machine and or store solely in the Cloud. Mega also provided point to point encryption, if you need more space you can purchase or try a different provider likely at a cost.

Depending on your mobility a NAS may well be a better solution, I have just set up a portable NAS with a Seagate Wireless 2TB drive on one of my Windows machines, no need for Cloud. To me the Cloud offers convenience, not security therefore it`s always prudent to keep a local back up, want to keep it safe, encrypt it.

Q-6

 

Selective sync for Dropbox lets you choose which folders to put on your computer.
https://www.dropbox.com/en/help/175#select

 

Sounds like you need a lot of storage. Get an NAS.

 

They will still be on Dropbox in the cloud and you can access the files with a browser. You can resync it later if you need it on your local drive.

 

You could use the Dropbox web client on your Mac.

Alternatively if your pc is on all the time you may want to try BitTorrent sync.