Random Iceland thoughts.
It's very expensive as nearly all consumer goods have to be shipped into the country. Food in particular is costly. However, the hot dogs are the best in the world. I ate them everywhere.
As I'm sure you know, all rivers are private and you have to pay to fish. Depending on the species you're after, this can get very expensive with prime salmon rivers costing over 1K/dy. I tend to fish brown/char/seatrout rivers to keep my costs down.
The other option is to get the Veidikortid fishing card. This allows you access to 36 lakes around the country. Just follow the rules in the book.
https://nat.is/veidikortid-fishing-card/
If you rent a car get all the insurance. Repair of vehicles is expensive. Some years ago, a couple got stuck in a river and abandoned their truck. Somehow they made it to the airport to escape the country but were stopped and had to pay the salvage and replacement cost of well over six figures.
Do not go on the F roads unless you have a reliable 4WD truck.
Here is a van I came across on the highway. The wind blew it over and as you can see they secured it with a concrete block to keep it in place until they could get a tow truck out.
If you want a few days alone, I would consider booking a self-guided trip in the highlands. You'll be camping and cooking your food, but you will be alone and have access to a lot of rivers and lakes. And you can fish at 2:00 am.
There are many great guides there so do a little research and pick who appeals. I used Heimar on my first trip to great success.
https://gofishing.is/
Tipping is in a grey area now. When I first fished there I offered a tip and the guide almost seemed insulted. "I make a good living," was his response. My understanding is that the younger guides are now accepting tips, so do your research on that.
Iceland is stunning and one of the most pristine countries I've ever seen. There are no billboards or power lines along the roads. Lines are buried and the best explanation as to no signs was, "Why would we screw up the beauty of our country?"
Here's an article I wrote about my first trip.
David N. McIlvaney Iceland is a Shangri-La for the flyfisher, but you can't be picky in your choice of fishing days. Sheets of rain? River flowing in a ...
www.gothamcanoe.com
Enjoy.