Hi
Will 3 rd Etosha. I am Cape Town based and have spent a fair bit of time in African park over the last few years. For a self drive Namibia is perfect, good roads, easy access to parks, good rental vehicles. Although for a windhoek ethosha trip 4x4 is not a requirement. Also the national park camp sites are very well equipped with cabins if needed, swimming pools, restaurants and bar.
The other great place in Southern Africa would be Chobe River national parks in Botswana.
But if you want to do Gorillas and cats perhaps staying in East Africa would be a better bet. Gorillas can be seen in Uganda, Rwanda or Congo, so cat side could be organized in Kenya or TZ.
Kenya has some very good parks and some of the smaller will virtually guarantee at the least lion sightings due to their small size eg Nakuru NP. For Cheetahs try Amboseli NR, also has heaps of Elephants. But for pureists this is not the same as seeing wildlife in huge reserves such as Ethosha.
Alternatively try a private safari where schedules can be tailored to your requirements. My friend run the South African arm of German Wigwam tour operators. He offers private safaris which are of very high quality so I am happy to provide you contact details if you want.
If your knowledge of African flora and fauna is not good, I would firmly recommend taking a good guide. As with most things the more you know the more interesting it becomes....for instance a herd of elephants is a herd of elephants but if your guide can explain the social interactions going on, the strategies they use to overcome drought heat etc, the whole experience becomes so much more rich.
Like most things it is dependent on how much time and money you would like to spend. How much your enjoyment is dependent on seeing specific wildlife etc
Happy tour hunting. Hope you have a great African trip
best Erol