If you can afford it, https://shade.inc/ or https://www.lucidlink.com/ are magic. Rather than downloading that 4K file entirely before you start, it will download chunks as you need them while editing. Avoids the NAS entirely, though you may want separate backups.

If you're local to your equipment (and can afford it), 10G local network with UNAS Pro. Search YouTube for "unas pro video editing" and there are various people discussing their setups. In this setup, your connection to the NAS is fast enough that file transfer speeds aren't such a problem, and the NAS software is nicer to deal with.

And, I know less about it, but you might want to investigate: https://www.blackmagicdesign.com/products/blackmagiccloudbac...

Finally, check https://www.reddit.com/r/editors/. Lots of good threads there.