Ah, the eternal question! 
Iām still very much a n00b to modular and finding (as many of us do, I imagine!) that all my initial ideas have either fallen by the wayside or been modified so much that they bear little resemblance to where Iām at now!
I have a 4u x 62hp Intellijel Palette which means I have to keep things pretty tight - my original notion for making (audio) signal flow dictate the layout is still there, kinda sorta, but has changed as Iāve added voices (currently Qu-Bit Chord v2, Erica Synths Pico VCO2 and Intellijel Dixie II v1).
That said, the heart of the current set-up (Bloom > Chord v2 > Pico sequential switch/2hp Verb) still flows left to right into the mixer strips, before heading ānorthā to the 1u headphones output. Introducing the VCO2 and the Dixie II has brought about a slight reversal of that, which Iāve come to terms with, and those are grouped more by function (VCO2/Arp/Delay, and Dixie II/VCA) before wending their ways across the case to the mixer. 2hp Clk and Div are more or less directly under the built-in mult, and find their ways out from thereā¦
Oh, and did I mention the 1u Radio Music�
[Cruddy screengrab from ModGrid then via Potatoshop to add the Radio Music]