We use inhouse on-premises email, issue tracking, and messaging. Depending on the project, external communication does require E2EE email. Development happens on local hardware and software unless required otherwise by the customer.
I’m pretty sure (even just based on the revenue of various SaaS products) that’s not typical, hence “most NDAs”. I’m also sure some require a SCIF, but that’s not most of them.
No this is still the level below needing a SCIF. The USG really tightened this stuff up in the 2010s and highly restricts what you can do with CUI. That's why there's a whole parallel FedRamp-compliant cloud ecosystem.
But in terms of how common it is, pretty much everybody in Fairfax County works in a company with rules like this; it's a big part of why the tech culture is so different than Austin or SFO.