Mozambique is not a province in South Africa! This means normal border restrictions apply! The border officials are not as relaxed as they used to be, so be careful what you take with you. You don’t need to take everything though, as you can get most supplies there.
All towns have the basic supplies, and the bigger towns like Maputo, Xai-Xai, Vilanculos and Inhambane have pretty much everything you need. If you want to take something, make sure it is red meat and dairy products, as they are more expensive than in South Africa. Just don’t overdo it.
You are only allowed to bring two bottles of wine or one bottle of hard tack into the country per person. Smokers should not bring more than a carton of 200 cigarettes in, but local brands are cheaper than in SA, and not bad at all.
Mozambique is probably one of the world’s best tropical holiday destinations. The people are very friendly and open, having put the civil war behind them. But it remains a third-world African country, where time is on a different schedule than what most first-world citizens are used to. Adjust your attitude and expectations accordingly, or you will be disappointed. If you treat all people with compassion, politeness and respect, the bribery and corruption that does occur should not affect you.