CSP for the past 5 years – looking the expand the repertoire prior to going to Europe this summer and hit a good sign up bonus with good rewards

Hey y'all.

I'm looking for some advice on which card(s) I should apply for next, as reviews have been making my head swim over the past few days. Planning a 2 week trip to Europe this summer and trying to maximize a sign up bonus, as well as looking at getting married in about a year and trying to make the right decisions now for that as well. I was thinking about trying to possibly get 2 cards, one travel and one balance transfer card with a long introductory 0%APR like Blue Cash that way I could BT my current Chase balance onto that card, shift all my usage onto a new travel card, get the sign up bonus, and then balance my current CSP card and the new "higher" card to max out my rewards earned over the next year.

I've kept just 1 credit card like the last 5 years and I'm probably middle of the road when it comes to CC knowledge. Before my CSP I did the CapitalOne secured->Quicksilver route before making the jump to CSP 5 years ago.

• Current cards: (list cards, limits, opening date)
  • Chase Sapphire Preferred – $17,000, July 2021; current utilization ~30%.
• FICO Score: 750
• Oldest account age: 15 years 8 months
• Chase 5/24 status: 0/24
• Income: $85,000
• Average monthly spend and categories:
  • dining $500
  • groceries: $400
  • gas: $100
  • travel: 0
  • other: $650
• Open to Business Cards: No
• What's the purpose of your next card? Maximize sign up bonus given the fair bit of spending I anticipate on this trip. 0 foreign transactions fees.
• Do you have any cards you've been looking at?
  • Citi Strata Premier
  • CapitalOne Venture
  • BoA Travel Rewards
  • WF Autograph
  • Very open to any other recs I haven't looked at. I don't know if I'll be able to break into the higher tier cards (Sapphire Reserve, etc.) at this point given my income but I anticipate that changing significantly in about 3 years so I'll make the jump at that time.
• Are you OK with category spending or do you want a general spending card? Prefer general spending, but OK with a category spending if the juice is worth the squeeze

Thanks in advance!