Whatever you end up deciding with, you need a MIDI-CV module that offers multiple channels, which already rules out µMIDI, since it only offers one channel of MIDI-CV conversion. Of course everybody here on the forums will tell you to get Yarns, I mean you’re on the Mutable Instruments forum but still, I went through a bunch of MIDI modules in the years and one thing which makes Yarns stand out to me is also the totally hassle free calibration. I mean, it just works and you don’t have to mess with trimmers on and stuff like that.
Regarding going with OT + MIDI-CV module or just a Beat Step Pro… well that’s a totally different question. To be honest, I don’t know if you can really compare the OT and the BSP in terms of sequencing, they’re really two different beasts. If you want power and lots of it (including 8 tracks, conditional trigs, etc.), the OT is your thing, if you want something more easy and more hands on (but with less tracks and more limitations) go with the BSP. I think it’s mostly a power versus ease of use thing, and you have to see where you tend to find your ideal mix of these two factors. BUt since you seem to already have an OT and seem happy with it, I don’t see why you should change. Keep in mind, the BSP is pretty big for what it does, so using it together with the OT is possible, but will make your setup more bulky.