If powering from the mains South Africa will also supply 240 volts so some adaptor might be needed for that.

With playing movies from the laptop, some laptops might be coded for a particular country eg USA, and some DVD software will be coded to a particular country/zone as well. Some software will allow say 5 zone changes until it is set. Probably ways around this sort of thing though. Relevant if you intend to buy some DVDs in South Africa as well which is a different zone from the USA. Thankfully most hunting DVDs are not zone coded. I forget which numbers are which.

PAL vs NTSC playback formats. Your DVD should be able to play both. USA is NTSC, most of the world is PAL.

I'm not up to date with what features to look for in a laptop so can't help there.

If you have a wireless internet modem (eg a mobile phone type connection) for your laptop, it may be able to be used in South Africa as well. Check with your provider.

A laptop for travelling? My main consideration would be thin, but robust, and light in weight!