If you have a dedicated GPS, tracks4africa is the best offline maps for the area. If you’re using your phone, Maps.me or osmAnd are two good offline mapping apps. Some people download offline google maps for the area. My experience is that almost all have one flaw or another. Google maps is getting better, but doesn’t have a lot of the smaller remote tracks. Other than T4A, all others occasionally list roads that are in fact only walking paths or motorcycle tracks. Less of a problem in Namibia than elsewhere.

You can’t stop anywhere, as most land is owned or managed by someone. Many people showing wild camping online (blogs, youtube, etc.) are either doing it illegally or very carefully. I don’t mean to be negative, just to paint the picture that behind every sweet instagram wildcamping photo is a backstory, and most were very careful about where they camped. The Crowther’s trail in the Palmwag concession offers very remote camps, that are undeveloped and effectively wildcamps (no facilities at all), though the actual location is designated. You get a permit at the gate and it is inexpensive, there are a half dozen camps to choose from. In most of Damaraland they are asking people to not wild camp (there are signs), though people still do it. Never camp in a riverbed, is is dangerous as a flash flood zone some of the year, and camping in the riverbed can block animals from water. I worry that irresponsible wild camping will lead to no wild camping at all. Dig around on blogs, find maps, look on facebook, and take everything you read with a grain of salt. iOverlander has many wildcamps marked, but many are illegal.

Some people bring a Satphone or GPS beacon (Garmin InReach), but it really depends on where you’re going. There is no cell reception in 99% of Kaokoland, but there is some here and there in Damaraland, it depends on how far you go. The issue with those devices is, who are you going to call? So you need to prepare a list ahead of time. The InReach might solve this, but it is not infallible.
Damaraland has plenty of excellent places for you to explore that are stunning and would be safer for a first time visitor. What time of year? Look up the rainy season (Dec-Mar or so). The riverbeds are prone to flash flooding at this time of year and can be very dangerous.
Check out the Brandberg Mountain area, Twyfelfontein is great. That area, often near De Riet, has desert elephants. Look at the Palmwag Lodge and Palmwag concession. Maybe check Elephant Song camp at the head of the Hoanib river. Warning on that spot, the track to get there is very very dusty and has a lot of deep sand. It is not a pleasant place to get the car stuck, because the sand is so fine.
Be cautious and learn or know something about navigation. You need offline maps, some sand driving experience and a plan B. Its a fantastic place, but also unforgiving of mistakes.

It’s hard to say. Have you done any 4×4 before, or taken any classes (a one day workshop will do wonders)? Are you going with another vehicle? Many would say to not go to Marienfluss or Hartman’s alone. I say you can, but only with careful preparation. It is less about how technical the track is, and more about how remote it is if something goes wrong. Those roads are very hard on vehicles and they’ll reveal weaknesses that you may not have detected on other roads. I’d recommend trying some of the tracks in Damaraland and getting a feel for your vehicle first. Is it your vehicle, or a rental?