When driving from Tzfas to Meron, you can stop at Abaye and Rava (and Rav Puppa)(oh and Rav Dimi 
! Very cool cave and simply incredible view also of the entire golan
For just the photagraphy of the veiw it's worth it, (It's about the best view i've seen in israel, maybe machtesh ramon comes close)
But it's ABAYA and RAVA!
Get a hold of either KADMUNEINU (
https://www.eyen-yaakov.com/product/%D7%A7%D7%93%D7%9E%D7%95%D7%A0%D7%99%D7%A0%D7%95/) or Rav YM Shtern's Mekomos Hakedoshim
https://yefe.co.il/product/%D7%9E%D7%91%D7%A6%D7%A2%D7%99-%D7%97%D7%95%D7%A8%D7%A3/%D7%A1%D7%A4%D7%A8%D7%99-%D7%A7%D7%95%D7%93%D7%A9-%D7%91%D7%9E%D7%91%D7%A6%D7%A2/%D7%94%D7%9E%D7%A7%D7%95%D7%9E%D7%95%D7%AA-%D7%94%D7%A7%D7%93%D7%95%D7%A9%D7%99%D7%9D/ which both have excelent maps of exactly how to get to all the kevorim, and how they relate to each other. also provide information on who the person was, some torah they said, special tefilos for specific mekomos hakedoshim, and what our mesorah is for how we know that this specific person in under this specific rock. There's also a Carta guide but i don't find it to be as good. (If you want to borrow mine you're welcome to come by in JLM, but it would be better if you look through them in advance).
With regard to all the kevorim there are in Tzfas/Meron/Tveria region, more is not nesseceraly better.
Decide which kevorim are meaningful for you to daven at, and spend your time there.
If you have a relative that needs a shidduch then by all means go to Amuka, but if you don't, I don't see it as a must see.
In terms of time,
I would pick up the car in the airport on landing. Israel rentals are very different from the states, and I don't think that you want to spend an hour plus (or +++, depending on your dates!) in the rental office on sunday morning!
Make sure you have a proper GPS app, preferably the Israeli WAZE and set it to avoid dangerous areas. Do not rely on the built in Openstreet GPS included in many rental cars. (My father ended up in Bethelehem proper!)
Random ideas:
The Chelkas Harabonim on Har HaMenuchs is impressive, it's like walking around on a seforim shrank.
Mekomos Hakedoshim (above) also has maps of Har Hazeisim and har hamenuchos
Gerer Rebbes near the shuk.
On the way to/from Kever Rochel, the Talpiyot Tayelet for great views of the old city.
Driving north on the 6 is much easier driveing and quicker, but the 90 will bring you through a very different part of EY. The 6 is a 3 lane highway, the 90 is undevided one lane each direction for most of it's length.
