A 10/5Mbps connection would be fast enough for a household where people have low to moderate data usage. You will have sufficient bandwidth available for at least one high quality video stream, but the connection might start to struggle if two people try to stream high quality/full hd video. There is a setting in the showmax app which controls the streaming quality if necessary.
Skype is capable of bi-directional video (standard quality) calls using as little as 1Mbps in each direction. According to their website, hd calls require about 1.5Mbps of upload/download bandwidth. Voip calls use much less data, typically in the 64-128Kbps range.
If you use Telkom as your LTE provider and want to retain the speed advantage that LTE have at lower price points, it might be better to buy larger prepaid data bundles every second month. The smart broadband bundles are valid for 61 days from purchase. E.g. you could buy a 120Gb anytime bundle at R759 which will give you an effective 60GB @ R380 'per month'. If you require more data per month, then a fibre connection starts to make more sense from a financial point of view.