Hello!
For context, I've heard the EP 4.7, the LS50, and Danny's Super 7 that uses the same open baffle neo3 tweeter from the NX-Otica (albeit in a wider baffle), but I haven't heard the NX-Otica directly. Based on how you describe the differences in your current speakers, I'd venture the NX-Otica won't be at all as harsh as the LS50, and although the EP 4.7 might have an edge in dynamics, the NX-Otica should be a more resolving speaker that can image very well (maybe a bit better than the EP 4.7, but the coax in the EP 4.7 might make that more of a 'different' kind of argument than clearly 'better/worse'), and might not be as forgiving on poor recordings as the EP 4.7 but (knowing Danny's designs in general) shouldn't be analytical to the point of not enjoyable and trades that bit of honesty for a big step up in refinement compared to the EP 4.7. Unless your main point of enjoyment from the EP 4.7 is big pro-audio driver dynamic range capability because of the genres of music you listen to, I think the NX-Otica might check many of the boxes you are asking about.
As for the subs, ideally a pair of OB servo subs would come along for the ride, but I don't see any reason you couldn't use your existing subs and do just fine with them until you feel the need/want to go open baffle across the entire frequency range. The advantage to going with the floor standing NX-Otica instead of the MTM monitor version of them is that the floorstanders can cross over much lower to the subs and blend well, so there isn't as much worry about missing out on the open baffle magic in the lower midrange/upper bass that the MTMs would need open baffle subs playing high to accomplish.
I haven't heard the Spatial X5, but a lot of people who's ears seem to align with mine have been very, very impressed with them and the other AMT-based models in the Spatial lineup. It is a very different speaker conceptually than the NX-Otica, and anything I'd have to say one or the other would really be just speculation, so all I'll say is that I personally wouldn't feel like I was taking a step up or down looking in to one or the other, but rather competitive products each with unique strengths; the difference in price is more about your sweat equity in to the DIY NX-Otica versus buying the X5 as a finished product.
If you've got the time, tools, and talent, the NX-Otica has been described as not just a flat-out great speaker but a whole lot of speaker for the money.