I hate to start another one of these threads, but I've spent more time than I'd care to admit trying to come up with an effective combination of credit cards to carry. I only do this about once or twice a decade, so I'd like to get it reasonably right. I've been scouring websites, running calculators, and reading posts in this forum, and I can't quite find the information I need.

Broadly, I'm trying to evaluate a few questions:

• Travel card or cash back card? I travel enough that if there is a way to tip the balance toward the travel card, I've tipped it. What I can't figure out, however, is how anything can be better than a flat 2% back (excluding the "5% if you can buy all of your gas in Q1 and all of your diapers in Q3" cards).
• General travel card or airline card? I used to have a US MC that got me 10k of EQM every year. AA took that away in the merger. Is there any real value anymore to having an airline-specific card? How much does that answer depend on what airline I fly?
• One card or two? For historical reasons, I have two credit cards with high limits plus my backup card. Are cards really so different that having two primary cards is worthwhile, or is the ideal situation a main card and one backup?
• Is AmEx really a thing? I keep reading about the AmEx SPG card, but I can't believe that carrying an AmEx card is really useful compared to VISA or MC. Is it?

Less importantly, in case you have any strong feelings, the cards I'm looking at are:

• Chase Sapphire Preferred (seems to be good for travel)
• Barclay Arrival Plus (seems to be trumped by Chase Sapphire Preferred)
• Citi Double Cash (how could anything be better than 2% cash?)
• AmEx Starwood Preferred Guest (everyone swears by this card but I can't figure out why)
• United MileagePlus Explorer Card (this seems to be the only US airline card that might be worth it, since I won't fly Delta)

I can find information on each individual card, but it's very hard to find direct comparisons. One site said that travel and restaurant spending can tip the balance from Barclay Arrival+ to Chase Sapphire. Another site said that travel spending can tip the balance from Citi Double Cash to Barclay Arrival+. The Points Guy calculator clearly indicated the Chase Sapphire card, but it doesn't include all cards.

Any guidance is welcome, even if it's just pointers to more reading.

Thank you!

-- Sal
smile.