Howdy! Been all those places. Have lived in CR for about 2 months over the last couple years. My .02:
Travel between towns in CR is far more challenging and slow than you'd expect. No real "highways"... twisty, poorly lit roads that shouldn't be driven at night. Traffic moves slowly. The drive out to La Fortuna/Monteverde (and between them) is beautiful.. but slow. Use Waze for reasonable estimates on times. Google Maps has a tendency to take you on "shortcuts" that are sketchy AF.
With that much travel you're kinda limiting your time to actually enjoy the trip. basically Travel Day > Enjoy day > Travel Day > Enjoy Day > Travel Day > etc. Some people may like that if your idea of a fun vacation is driving, packing and unpacking, checking in and out. Me.... not so much. For 1 week I'd factor in 3 stops MAX.
Regarding your destinations: You're hitting a lot of very touristy areas. That's not a bad thing, but if you're going with the intent of experiencing real Costa Rica & it's culture, you're not going to get that.
Then again, I also think people who go to CR for All Inclusive Resorts are silly and doing it wrong, as well. So that bias should be known.
Playa Flamingo: Upscale touristy little beach town. Only spent a little time here while staying In Playa Hermosa. I preferred Playa Hermosa, personally.
La Fortuna: Cool little town at the foot on Arenal Volcano. Lots of hot springs, a cool park, some solid restaurants, LOTS of tourist crap.. shops, people hawking stuff on the street (and drugs), etc. There is an incredible guide there, Carlos with Carribean winds (
https://caribbeanwinds.tours/) . Can't recommend him highly enough. If you want to see wildlife, his river safari float was one of the highlights of our trip. Arenal is a fun hike (El Silencio), and the public hot springs in the river are chill... but if you guys are high maintenance then you'll likely prefer the spas at the resorts.
Monteverde: Beautiful spot. VERY hilly. Selvatura Adventure park (
https://selvatura.com/) is the spot to scratch your Cloud Forest / Zipline / Hanging Bridges itch. Hummingbird garden there is awesome too. We stayed at Valle Escondido Eco Lodge (
https://www.valleescondidocr.com/) and really enjoyed it. Wildlife around the property. Beautiful views at night. Nature hikes on property. Great breakfast and adorable little rooms. Also the San Lucas Treetop Dining experience is a cool one (
https://sanlucas.cr/) . Not cheap, and the food is more interesting than amazing... but it's a great experience everyone should try once.
Tamarindo: I don't like Tamarindo. There's a reason locals call it Tamagringo. If your Idea of experiencing another country is to Enjoy Americanized food at American prices, paying in American currency around a ton of gringos... You're going to LOVE Tamagringo

Spent a week here and the whole time we wished we were anywhere but here. Beautiful Beach. Great sunsets. That's it. Problem is, there are dozens and dozens of towns with comparable beaches and sunsets for far cheaper and far more "Authentic" experience.
IMO I'd consider
D1 Land @ LIR - Drive to Arenal.
D2 Full day Volcano Tour
D3 River Safari Tour w/ Carlos
D4 : Drive to Monteverde > Treetop Dining
D5 : Selvatura Adventure Park > Dinner somewhere
D6 : Drive to Playa Samara or Playa Hermosa (Playa Flamingo would work too!)
D7: Chill... Go fishing... Do a booze Cruise.... whatever..... Go to Dinner
D8: Chill... Go fishing... Do a booze Cruise.... whatever..... Go to Dinner
D9: Drive back to LIR