Can you clarify what you mean by best version? There are hundreds of volumes, and I'm not sure if you're asking which has the best coverage, information, transcriptions, availability, etc.

For example, Henry VIII there are: Letters and Papers, Foreign and Domestic of the Reign of Henry VIII, 37 volumes in 21. Volume 1 was replaced by 3 parts in 1920. All are available on HaithiTrust, and most should be on Archive.org or Google Books.

State Papers of Henry VIII 11 volumes. These have fewer entries than the above Calendar, but the ones that are printed are more fully transcribed. All are available through Archive.org or Google Books.

Calendar of Letters, Despatches, and State Papers...Spain Volume 1-8, & Supplements (Volumes 3-6 are in two parts each).

Calendar of State Papers and Manuscripts, Milan (1385-1618) Haven't found one that's free, but TannerRitchie has a digital version for ~$20.

Calendar of State Papers and Manuscripts...Venice Volumes 2-5, All available through Archive.org or Google Books

Calendar of State Papers Relating to Scotland Volume 1 (1509-1589) Google Books