I have an original Mac Pro 2010 with 64GB ram. I want to run Windows Server 2016 on it.
- What would be the fastest SSD I can use for booting to Windows, which is equal or larger than 512GB?
- Which M2 card would work well?
Just get any SATA SSD that has the capacity you want. In the real world you won't notice any difference between different types of SSD, especially not for Windows once you have a few updates on there and some applications.
As with CPU's for every day stuff we reach a point years ago where SSD's were fast enough. You could pick up, for example a 2010 MBP with a SATA SSD inside and it would be fast enough for web browsing and running a few VMs. You may get short on RAM, but the storage would be able to cope with what you are wanting it to do.
So if I were you I wouldn't over think this, I'd just get the best price I could on a 512GB or 1TB SATA SSD (Samsung, Western Digital or some other quality brand) from a good supplier and have done with it. Spend your time thinking about something else. SATA would also be the easiest to install in your Mac Pro.