Theoretical Rack Talk

I would say You're kinda blocking yourself with the further expansions. I would leave some space in the rack for later additions. There are some more modules fitting Your purpose already: 3VCSWITCH, LOGIC, TRIQ164, maybe also LOPAG, NOISE, MULTIFX. And with some more modules comming soon who knows with what Robert will treat us? We already know Sample player module is beeing prepeared - perhaps You would like to put some additional drum sounds into it? Like tabla or anything else? 
It's for You to consider, but many of us here bought some set initialy and wanted to have more at some point, so I would recomend to be prepared  

Regarding expansion from arti, its very intentional to start small.  I have 19" rack room, so when I do expand the AE footprint, I'm thinking of building a rack from scratch that would then mount into 19" rack. An alternative is the standard width case at ~16.26" wide and adding rack ears. I'm still thinking about things, but I like the idea of the small case. I think it would let me break out modules and let me focus on them in a different way compared to having a large rack that might overwhelm me.

I've found playing on grid.aemodular.com/ was that whenever I selected a case, I'd fill it to the brim....So expansion is likely in my future, but I think I should take baby steps (also for my wallet's sake).

As for MIDI clock, admin I think you're right since I sync all my other stuff via MIDI and have an iConnectivity Mio10. In trying to stay small, I thought having 1 module for power, 1 CV, and headphone output then another module with just 4 I/O would be more flexible. Since the Deluge is my sequencer for everything else, I was thinking I would just use a gate out to act as the clock for the AE rack. I didn't think about MIDI start and stop commands, but wouldn't an AE system just stop receiving clock and just stop itself if I hit stop on my Deluge?

I'm thinking of the order of the modules and I don't really have a clue on the best way to do that yet.

At the same time, though, having a few more filters would be useful for electronic percussion. After all, some of the most classic electro sounds are created with "pinged" resonant filters. And it's easier to work with them in a modular setup than trying to lock up an old-school rhythm box to your main DAW sync clock. It can be done...but that requires some extra toys like ultra-tight filters for beat extraction, something like a Time Bandit to change audio to clock pulses, etc.

When the time comes for expansion, I'll build or buy another case, so I'm not too worried about it. There are financial considerations with starting smaller as well. Music is definitely a hobby and I wanted to try to design a rack that fit specific needs: generative drum patterns, introduces me to the AE format, relatively inexpensive, and fun.

When I first started playing around on the grid page, I definitely would start with the largest case and proceed to fill everything. So I definitely am aware that there are many ways to grow  . I mean I'd want a noise generator, some more oscillators, envelopes, more filters (all of them)...But you gotta start somewhere and this is a way for me to just get started.

Sync'ing will occur from my Deluge. I sequence all of my stuff from it. The I/O from the rack will let me do a lot of control from my Deluge's 4 gate and 2 CV outs since everything else I am using is completely MIDI.

Plus, as Lugia pointed out, there are more modules that are eventually coming out that are very interesting. And this smaller case can be very convenient as a side rack down the road as a controller or just as a way to experiment and focus on a handful of modules at a time.

Thanks MikMo about the comment about the filter. I didn't know the resonance on that filter does it to such a degree. Would you recommend the SVFILTER over the Wasp type for drums/percussion? Ideally I would want them all, but it would be a good idea to consider what the next steps might look like (after I get the rack and play around with it). The LOPAG was another contender.