Hiya Nick
I'll confess I don't use all of them all the same time. The reason I have them is more for the different functionality they each provide and I generally unpatch everything apart from that main signal flow I described for clock and reset throughout the system. I do this because it helps me learn different and new techniques and helps me build my knowledge by repeating the act of patching things again and gain.
Sometimes I use the RCD as a way to trigger the reset of the Metropolis which can really provide a nice change to the sequence from the metropolis along with everything else that this module provides.
However that being said, it generally depends on mood. If I want to start something fast, my goto is the metropolis. If I want to do something more intricate and happy to spend time on the sequence, I use the Hermod with its effects. These two modules tend to be starting points for sequences that drive the melodic structure of music.
The mimetic, clep and zularic is generally used with the Squid Salmple and the BIA for cv and trigger inputs. Sometimes I may use a Quadratt in the path to restrict the range of the voltage going through on the BIA to get a more subtle modulation of one of the functions. Mimetic is fast and gives you really great percussion type random variations to the BIA as well as on the squid with a click of a button. Zularic helps in creating interesting rhythms that are derived from world music which sit well with a standard 4 to floor beat. If I want euclidean patterns I can get those from the temps or hermod too.
Predominantly though, I really like using sequences in the cv input of vca's and also in the trigger inputs of the Quadra for envelopes which then go into the modulation inputs of filters. I jut seem to get better results and more control that way than using lfo's .
I tend to use the temps and ll8 for even more control like when I want to exactly trigger something to happen at an exact point based on me manually sending a trigger to something else.
In a nutshell though, I just love sequencers for modulation and not just for driving the melodic structure of music or what sound like music to me :)
I am planning to write a longer post which I keep meaning to do comparing my rack now to the original advice I got from Lugia which was great starting point for me, and I couldn't have done without it as to be honest, I remember not fully understanding right at the start why Lugia had organised my rack the way he had at the beginning of my journey into Eurorack. Like I remember Lugia putting an Octane into my rack and I was like what is that thing useful for, whereas now I have like lots of Octane type modules :)
Another aspect is cost, I think it's worth investing in the extra modules if you can get them for good prices. For example, I bought the analogue solutions generator for £265 and the zularic repetitor for £80. Prices were too good to refuse and my thinking is I could always sell them on if required and not lose money on them
Another example of a patch is to take a lfo from ochd into the rotate input of RCD, this way the clock divider will be generating different rhythms which you can use as a trigger in of the Quadra. You can then use the output of that as modulation to the filter but its generally things of that ilk.
Oh and why the two varigates - I guess this is because I too like to decouple gates from sequences so have one in gate mode and the other in cv mode to give me that flexibility.
Hope this helps :)