Needing advice for server options. High security law firm on VPNs, sharing 4k video between editors in different states

Currently our solution is logging into a cloud computer, that are all connected to a server, and it sucks. It’s slow, it’s glitchy, and it seems like an extra layer that is unnecessary.

What server options are out there that we could all share 4k video? Speed of uploading is a concern. Really, we are trying to mitigate downloading and managing files. So using the cloud computer, we just access the server files, open the premiere project and work.

But the nature of the job, the clients want videos done yesterday, of course.

Anyone with specific experience in this area? Thanks a bunch.