Hi Kelly,
Cool itinerary, those are some of our favorite places in CR!

On the 4×4, you should probably get it because you’ll need it for Santa Teresa/Mal Pais. After Naranjo in S. Nicoya, the road is paved part of the way and dirt others, with some very hilly spots with loose gravel. The last 20 or so minutes of the drive was really bad last time we visited too- we even decided to rent an SUV to avoid wear and tear on our own if that tells you anything! Here’s a post we did on our trip with directions and more about road conditions: https://www.twoweeksincostarica.com/road-trip-to-mal-pais/

Depending on the size of your group, you could keep the car for La Fortuna and Santa Teresa where it’ll be nice to have and then ditch it in Quepos/Manuel Antonio. If there’s just a couple of you, the shuttle to Sierpe (place where you get boat taxi to Drake) will be less than $100 total, and you can just fly on a small plane through Nature Air or Sansa direct from Drake to San Jose afterwards (super time saver and inexpensive if booked in advance). But if there’s 3 or more in your group, it will probably be cheaper to just keep the car so you can drive yourself/save on shuttle and leave the car in Sierpe while you’re in Drake Bay so that you have it for the drive back to San Jose. 

That said, there are some cool places to explore with a rental car around MA (Rainmaker Reserve, La Iguana Chocolate, etc.) so if you do decide to ditch it, maybe keep it for a day or two there to explore then chill in town for the rest of your time. You definitely don’t need a car for Drake and we don’t recommend driving. The roads getting there are rough with river crossings, and once you get there, you’ll see that most people don’t have a car and get around on foot. We just did a post on Drake Bay that covers all of this and more if you’re still looking for a place to stay, etc: https://www.twoweeksincostarica.com/drake-bay-costa-rica/

Hope that helps!