Using containers with many merged train loading chests seems to cripple UPS:
https://imgur.com/a/oa10m3T
It doesn't matter whether the trains are actively loading; UPS in both screenshots is steady over time. I imagine it's because many chest slots (like a warehouse) are being checked constantly. Would it be possible to reduce the container signal refresh rate or disable some of the default signals in mod settings? Disabling might also be helpful for getting just the real item signals when checking > 0 satisfaction.

Yeah that looks pretty bad, do you have a screenshot of what you're referring to with your trains?

I overhauled the original blueprints to not use containers. The main use case was a delivery stop with a merged long passive provider chest on each side, each wired to its own container, and set limit = 1 when S > 120 (out of 160 total for 1-4 trains). Pickups used a pair of merged long buffer chests, also on each side, and either a roboport or 2 containers to read contents for controlling power switches. I had around 50 stops of each type with the train leaving pickup when cargo full and leaving delivery when empty, and only the train stop icons varied. Here are the last several saves from before I uninstalled containers. I can't load them now myself without running out of memory (4GB+/8GB total) and hanging Windows, back then it was somehow possible with around 95% RAM usage.
https://drive.google.com/drive/folders/1XcztSm8xJnfGvhvXWW-FNQmXl5kD1GzA?usp=sharing

So I didn't use your saves but I started running into my own issues. I think that I've got a solution in fix that helps make it reasonable. Take a look and see if it plays better for you.

If it's still a problem I will look to add a refresh rate for things.

Looks better, this is the equivalent of 50 empty train stations/2 sided unloading or 100/1 side. Max UPS of the mod is between 3 and 6 with items inside; overall still 60.
https://imgur.com/a/rMzPzVZ

this mod overall iterates thru all its combinators and all chests every tick.
thus, not usable on gigabase level at all.

sadly =(

yeah if there's a better way I'm struggling to find it. Let me think about it

might not be much different but worth a try: remember container id of the CC and trigger update only on container content update.

There are no events to know when a container's contents are updated.

But, I've improved the logic on this to only update containers 1 out of every 10 ticks. It uses a bit of math to determine which subset of combinators to update on any given tick so there shouldn't be spikes. Let me know if this makes any improvements in your large scale factories.

maybe use a similar system vanilla does with logistic chest content? it processes a LOOOOT of data and doesn't use that much UPS. also SE has some elements like remaining space/used space on their rocket silos.