Question Dry suit sidemounters, how do you route your suit inflation?

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Most of my muscle memeory came from diving backmount, so I still keep everything on my right hand, while only having my light on my left

Now, if you want to raise your hand in front of your face to look at your gauges/computer without venting gas, then maybe you want to keep those gauges on your right arm. Hence light on the left. Also, if you have a long hose and want to donate it, then it's done with your right hand, isn't it? Your light is best kept away then. This is true both for bm and sm.
- I'm sure there are other diving styles; this is but my preference

and I use minimal movement with my right hand to inflate my wing or suit. While I dump air with my left hand. So it was logical to have it split between left and right like that to a (primary and secondary cylinder).

Both cylinders are very much primary.

In sidemount diving you need to switch regs every X minutes or every Y psi to make sure the pressures remain very close to each other. More buoyancy on one side does generate torque and fighting that strains your one leg and this can lead to muscle cramps. Yeah, been there. Didn't watch my SPGs and got leg cramps and it was under solid ice. You can guess if that was my happy place. Hint: breast strokes are a valid method of propulsion in sidemount diving

since I donate the right tank (secondary), my primary buoyancy is my wing, so I figured it's supposed to be on my primary tank which will never be donated. And I can attach both my drysuit and my wing as needed if I have to donate my left tank.

Donating a tank might happen in a restricted cave environment without long hoses. It has surely happened.
If you dive dry and wear steel tanks to replace some of the lead (or to withstand the hardship of sump diving), then donating a tank would be unwise. Long hoses are great.

 

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That's Old school Sump style configuration?
I always find it cool! But looks highly specialized.

I don't think it is highly specialized. I find it natural to have a left hand side reg that is attached to the left bottle. Etc.
Regs, bottles and SPGs do match then.

Besides, having this old school neck bungee that supports both regs, one on each side of the chin, removes the need to clip/unclip regs when changing.

Personally, I find the Apeks sidemount setup to be an attempt to replicate backmount setups. But for what reason? Yes, some people say mixed teams, but in my opinion, know your buddy is better. And I really do not want to unclip/clip a reg ten times during a dive.

Now, if you love the "all regs on right" setup, then fine. Sidemount diving is a tool and whatever works for you is great.

 

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Have you ever tried to totally unclip a steel, set it down, and see what happens? We did this during my SM class in a pool, 4ft deep. Headed straight for the surface. So no go to hand off a steel.

Yes, I was a helping hand at a SM diving course (and, um, seemingly the most skillfull sm diver present as the instructor wore backmount doubles). The instructor asked the students to ... unclip 12 litre 232 bar steel tanks ... that are somewhat negative ... it was as hilarious as stupid. While buoyancy did not change, the distribution / of it did. Wetsuit + aluminum tanks are one thing. Drysuit + steels is another. It's great to reach for the heavens - with your fins, right?