My thoughts: RGB is high risk, high reward. Frustrating at times, but very gratifying when done right.
First off, be sure to get your mind wrapped around some decent software. It is still the weakest link. I took to LSP like a fish to water, but many don't. Try them all and decide for yourself. LSP would allow any configuration like folding. That said, I keep it simple. Folding creates confusion and unnecessarily complex setups when adding new sequences. There's no getting around it, you will need to splice and add connectors. Split the string in 2, creating 2 50 counts. Run each to a zeus string.
I think a 360 degree mega is overkill unless it can be viewed 360 degrees. I would advocate 180 degrees for most displays. This drives cost, complexity, and channel count down drastically. Zeus is THE controller for a mega. I think a zeus with 16 strands is perfect for 10'. While I've not added one myself. I have spent much time and effort designing one and coincidently enough it is 180 degree, 16 strands, single zeus. Think I went 32 nodes a string though.
Now that you mention arches and minis, I run multiple zeus for ALL ground elements since I lost many SSCs from water/snow last year. My fault, most just laid on the ground... KEep in mind they need to stay close to the element. Also, heads up the modules will need power injection.
Ramble off...