My suggestion is a little bit different from others:

AMEX:

• Blue: Convert to Amex Everyday
• Everyday: Closed if Blue can be converted
• Costco: Stay as-is

It sounds like that AMEX Blue is an older account than your current AMEX Everyday. So it is best to keep the older for AAoA and you can close the new one.

Since AMEX Costco will be transferred to Citi. You should not do anything at this moment until the transfer is completed, even it means you want to cancel the account.

Chase:

• Ink Bold: Stay as-is.
• Freedom: Close or switch to CSP (product change or new application)
• United MileagePlus Select: Stay as-is or Close

Ink Bold is good for office supplies (OD/OM/Staples). So it is a good card to keep.

Freedom is an average no-AF card. It is good only if you can maximize the quarterly bonuses. Other than that, it is a typical reward card. I would rather use something more definitive, like CSP if I can justify the AF, or Citi Double Cash for its simplicity.

MileagePlus Select is a good card only if you are a UA Premier member or you don't mind paying the AF. Other than that, M+ Explorer card is a better card as it can give you actual benefit you can use.