These kinds of lists are tricky as something like Wolfberg Arch is an easy day hike for some and a really hard 2 day hike for others. If you look at Drakensberg equivalents - some people find the Northern High Traverse to be a difficult 7 day hike while the speed record for a full Drakensberg Grand Traverse (more than 3 times further) is sub 2 days. Nonetheless:
Waaihoek to Fairy Glen Traverse in the Hex Mountains is awesome. 2 to 4 days (probably doable in a day, although it would be a big day), huts, difficult. No trail between Pells Hut and Fonteinjies, but marked by cairns. Amazing route, highly recommended.
If I remember correctly, the Swaartberg Traverse Hiking Trail is a 3 day with huts, but I haven’t done it so I can’t comment on how difficult it is.
Bokkeveld-Sneeukop is also usually done over 2 days, although we did it in about 6 hours and found it fairly easy. Tents.
Seweweekspoort from Ladismith side is often done in 2 to 3 days, with the cave as an option. Probably on the more difficult side, but I did it from the north, so I can’t confirm.
But there are tons of multiday hikes around WC that fall into those specs, coming up with a complete list will be really tricky.
In that case - unquestionably include the Waaihoek to Fairy Glen Traverse in the Hex Mountains. It isn’t easy, but is absolutely amazing. I did it in two hikes a year apart, doing Waaihoek to Perry Refuge and back in 2020 and Fairy Glen to Perry Refuge and up Buffelshoek last year. Writeups with photos as follows:
Its not for everyone, and I do generally avoid it where possible. But a lot of the reasons quoted for why it is a bad idea are actually not relevant. Notably on this particular hike there was another group nearby as well as signal for most of the route - so if something went wrong (aside from taking a fatal fall, where being in a group wouldn’t have helped anyway), I would have been able to get help fairly quickly.
Generally most problems with solo hiking come from people who aren’t sufficiently experienced. I have been hiking in the mountains for 13 years now, with approximately 10 000km of distance covered in that time. I’ve made enough mistakes to know what I’m doing. As the old saying goes “Good judgement comes from experience. Experience comes from bad judgement.”