It can be tempting to put modules from the same company together because it looks nice when the modules match in appearance. That's what I did when I first put my rack together, and I still try and do it when it makes sense, like having similar or related modules next to each other. But what worked better for me as an overall plan was thinking in terms of work flow and function.
I have a large case, it's roughly square but I mentally divide it into two parts. The top two-thirds (roughly) is devoted to audio modules and the workflow goes left-to-right. The left side is sequencers, oscillators, and voices. Middle is envelopes, filters, reverbs, delays, and so on. My main mixer and output module are on the right side. The bottom third of the rack is VCAs, LFOs, modulation sources, and most of my utility modules. So basically the audio signal goes left-to-right across the top and middle of my rack while the modules at the bottom pertain to CV, and/or are the things I fiddle with the most often, like VCAs.
That makes me wonder how you arrange your cases; if I had a tall narrow stack like in your pic I might think more about top-to-bottom workflow rather than left-to-right, but perhaps you just arranged them like that for simplicity in modulargrid. How do you actually have your cases set up when you play? You also mentioned portability. That makes me think it might be a good idea to set up one of the Intellijel 7u cases as an all-in-one mini system so you could take just that one case if you wanted to be extra portable, and then you could arrange the other cases around the idea of expanding upon the capability of the core one.