My experience of slap is quite limited As my musical background went prog > punk > new wave. I briefly enjoyed Mark King but to me (imho) it’s very fast clicky and utterly soulless, it might be technically brilliant but it doesn’t move me. There are some Level 42 tracks where he does some finger style stuff I like but it’s a brief glimmer of sun before the clackity clouds come in again. Likewise Stanley Clarke doesn’t move me much either, it’s probably just not my bag. Mind you, having said all that, new wave is peppered with little slappy odds and sods ...
... Paul Raven would slap occasionally, I asked him about it once. “It’s forgivable as long as the thumb isn’t upright, that’s a signal, an upright bass slapping thumb is a signal to Satan notifying him of a soul ripe for harvest.”