My wife and I visited Iceland for 2 weeks this year. Absolutely great. We hired a Vivaro camper van, which meant we couldn't do the F roads, but there is still plenty to explore off the main island ring road, plenty of dirt roads, many not over used but easily drivable. Would recommend exploring the western area, the bulk of tourist traffic does not bother as it can take some time and a lot of miles to cover a short distance as the crow flies. Free camping is illegal, which is a bit of a disappointment, but I can understand why. I think the main thing with fording on the F roads is the flow of the water, the depth will depend on time of year and be at its lowest towards end of summer, spring in the thaw would be quite hairy.