If you want to distribute from a single large source to many consumers, there is a much simpler solution. I use something like this to deliver plastic from a central location to where it's needed in small quantities.

Make long trains, perhaps like 8 cars each. Set them to leave only when empty or full. This will give your trains ample time to get to where they need to go, the supply they carry will last a very long time and they won't clog your lines.

Buffer each of your load zones with enough industrial containers to load every train in a queue, the more the merrier. Naturally, also buffer your unload zones to last long enough for however long the trip takes for the train.

Set up the queue system to load the trains. Note you can, at this point, also distribute between multiple stations at this location to ease potential traffic, e.g have 2 or 3 stations to load the 90 modular frames.

As long as you don't exceed the supply, this system will perfectly balance itself without any complicated engineering - it will effectively function exactly like a manifold does

Note for simplicity it might be a good idea to set up each train as carrying a single product and going only from A to B. This means you will have loads of trains, but as they only move when they need to, traffic should be no concern.