Can I efile my personal return today or must I file a paper return?

You can efile until Midnight today Oct 15 your time zone.  If it rejects you have until Oct 20 to fix it and resend it.  Otherwise you will have to print and mail it.

You can e-file until midnight tonight (Oct 15th). After doing so, you'll get 2 email confirmations (first one confirms that you've filed, and the second one will confirm the IRS has accepted it - you might not get the 2nd email until 48 hours later, but you'll more than likely get it within a couple hours of e-filing).

You don't have to paper file/physically mail your return.