Both are in Account Settings.
Signed-in devices → Sign out everywhere ends every session on the account: every browser, GridCast TV, and the Broadcaster, Lite and Launcher apps, including the one you're using. Use it if you signed in on a computer you no longer control. Changing or resetting your password does the same, except that it keeps you signed in where you made the change.
Your data → Download my data saves a JSON file of everything GridCast holds about your account: your profile, league memberships, results, channels, teams and the rest. Passwords and sign-in tokens are left out.
Preferences is where you set your timezone and choose whether to get GridCast news and product updates by email. Receipts and account notices are sent either way.
