Do not apply for 31 cards, that likely would result in about 25+ denials and likely a few of the newly approved cards to be closed when they see the 31 inq on their ar softs.
From my experience most lenders will auto deny you if you apply for more than 2 cards with them(or less) or if you have more than 5-6 inq in the last 6 months(or less).
US Bank is very inq sensitive so that should be first if you want it, followed by citi\chase\bofa, navy seems fairly lenient but have no 1st hand exp and amex at least for me was pretty lenient with inq count (approved with 7 in last 6 months)
I would choose no more than 4 at the very most but would highly recommend waiting until you get that last collection off if you expect it to be removed soon in order to save yourself from all the inq.
Given your history, I would avoid the signature cards as they require 5k limits generally as well as citi (prior co) and penfed (high high credit requirements). Consider one or two of these:
Navy Federal Credit Union Platinum Card
American Express Zync
US Bank Cash+ Visa Signature (no annual fee and good rewards)
Barclaycard Rewards World Mastercard (no annual fee)
Bank of America BankAmericard Travel Rewards Visa Signature Card (no annual fee)
Why not? What's stopping you? I'm just kidding. Yes, you probably shouldn't.
Which categories do you spend mostly? You have quite a few travel related cards in your list. You mentioned you fly Southwest domestically, but is it a lot of traveling? If not, I would skip those. PenFed has a 5% back travel card, but I hear they are conservative.
I wouldn't apply for too many cards with annual fees unless my usage would justify them.
Depending on if I'm on my own or living with my parents, I would only apply for 3-5 cards.
Based on my spending patterns, my list is below.
Citi Forward Visa (I purchase from Amazon a lot)
US Bank Cash+ Visa Signature (choose your two 5% categories)
American Express Blue Cash Everyday (backdating in the future)
I would throw in a credit union somewhere in the mix (you may have a hard inquiry to join and another for the card application) and a Barclays Ring card to my list even though it's not on yours (low interest rate in case I need to finance something).
Good luck, and let us know how everything turns out!!