Cannot tell ya'll how important checking the road conditions DAILY is, if not more... We went from summer to winter, back to summer and hurricane-like winds thrown in for fun... www.road.is is you friend. Also, a hotspot in the car is wonderful.
I drove over 1800 miles, saw so much and left so much yet unseen. Plans had to be changed so another tip I would add to you self-drivers out there is to 1: make a plan, then 2: make an alternate plan just in case things change, like the weather... RS guidebook most handy as well- I ripped out the parts we did not need and left them at home as we skipped downtown Reykjavik as well as Myvatn.
If you would like to see our travel diary you can view it here: https://blindhogandacorn.home.blog/iceland-travels/ It was an awesome trip...