As far as I know, there isn't a hard limit on the number of features. I've worked with parcel datasets that have millions of features, and there are plenty of layers in the ArcGIS Living Atlas that are at the national scale and have feature counts in the millions as well.
That being said, there is of course a "practical" limit of how many features the browser can handle, and you'll most likely run into performance issues when you work with a layer that large. But it seems like you have a workflow in place to work around that and create views, so that's not an issue for you guys.
One other thing to consider is of course credit consumption if you are hosting a feature layer that large in ArcGIS Online. But those limitations will vary between organizations.
Best,
Katie
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