#1 Attraction IMHO is Plit Vice national park. You need to buy tickets in advance for specific times/days. It is best to enter the park right when it opens. Avoid all the tourist crowds on the boardwalks.

Then you've got to debate if you drive down to Mostar Bridge (Stari Most) in Bosnia.

Or go up and visit Lago Bled in Slovenia. Or Ljubljana Slovenia.

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Then 1,001 things on the coast!
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We rented a car and it made travel in Croatia fantastic! except for worrying about traffic cameras. be sure to understand that approaching cities, the speed automatically changes without a posted change in speed. Learn how that process works.

Also for internet you can get a sim card from the kiosk in the airport (Zagreb) that is good for 10 days with unlimitted data.

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Zadar will have Kresmir Cosic statue/arena.
Split is a major tourist/beach zone.
I have a recommendation for a sleepy island AirBNB in Trystenik.

Dubrovnik is worth seeing...

Way up north you have areas like Pula and Rovin in the Istria Peninsula. (We didn't have time to see that area).

Be prepared to see a lot of VERY tall people along the coast.

We also briefly spent some time in Zagreb and Varazdin. Lots of charm. You can tell that tourism money is transforming Croatia.

The A1 is the fast path north and south by car. Tolls are nominal.

I'd also say a brief drive of the coast between Dubrovnik and Split is worth it. Drop by Ston for the stone wall and not far off Trystenik