The whip does not replace walking. The whip was a placeholder and is used to apply scar textures (if you have them enabled), and if you use SLSO and train the chastity belt, at some point during whipping you can gain the Pain Slut power, which allows you to orgasm during special masturbation. A long time ago I had the Pet Project mod, and in order to have a way to cum during permanent chastity, I came up with this idea.
As for NPC selection, I think the better option would simply be to add a spell called “Add”, but I play very little with NPCs and I’ve never really tested how it works. Still, it would definitely be nice to add some alternative form of training — maybe whipping, for example?
Do you have a problem with slow motion in the latest version of DT? I think I removed that from DT quite a long time ago. I haven’t checked the game files for this yet, but requests to remove it already came in a long time ago, and since I myself started getting irritated by that mechanic… can you confirm that you experienced this effect in the latest update?