Sharing answer from PM here for everyone:
Last year (this time), Ian (who works on webcore on ST) and I made updates for both ST and HE that sends devices from the webcore groovy app to the IDE/browser in chunks.
So this should allow on both sides (ST or HE) for a single webcore to work with many devices (and it does not try to send all the devices at once which caused ST to timeout due to the cloud limits).
So I think you could try to do this on HE with a single instance. If you wanted to break up dashboards, you may want multiple instances, but I don't think you would need to do this at the start.
I have ~120 devices in my environment with no issues, I have seen others with more.
So you can give this a try, and if there are issues we can look into them.
In general a single instance on a single HE system is likely to be better for resource consumption.
On HE, some folks run multiple hubs in their environment, and break things up that way. This is not so much related to webcore, as to the memory available in HE for running things, and if a hub starts to run out of memory, things get wonky.
How to see memory on your hub:
