I'm a newbie with some technical skills, but not a lot.
Should I be using MetaMask for added security?
What does MetaMask do for me, exactly?
Also, MetaMask seems to only work for Ethereum-based coins. Is there an extension like MetaMask available for the other coins?
you must always use Metamask where its required.
I am mostly using Metamask while I trade on ETH based DEX like etherdelta, etc.
Pros of using metamask:
Your private key remains with you in your browser and is never shared with exchanges.
Usually they have a list of phishing websites maintained under radar, so if you mistakenly visit any sch website, it warns you and save you from getting hacked.
Cons:
Only for ETH based tokens
Do not have 2FA