Let's talk photo/video sync

So with Google photos app now giving you unlimited storage to sync. Or 14GB for full res....
Is it worth using? Or are their better alternatives?

Also as it syncs what's on my phone if i delete something off my phone does it delete from the photos sync?
If so, can you/or is their other apps that allow you to delete from your phones storage but keep online and be viewable in an app like quikpic etc?

I've never really looked into this before and I'm sure their are many others the same as me. So let's talk like it's a kinda beginners guide off all we need to know

Thanks everyone for any help/info

Sent from my Nexus 5 using Tapatalk