1. Google Music lets you keep your music on their Cloud, and it's MUCH bigger than iCloud + for free.
2. 'MEGA' app installs on your iPhone, saves every photo you take to a Cloud that takes no space on your phone, is for free, and it has a password lock if someone tries to open the phone. You can then access everything from desktop on Mega's site.
A cloud is just useful for keeping photos + music. Oh, and Dropbox makes your photos public.
No. I have 350 GB on OneDrive thanks to my previous phone and tablet (Lumia and Samsung) giving it as a gift, and once MS just gave me 100GB like that. I'm sticking with them.