Regarding which Elizabeth is the mistress of James V, doesn't this suggest in the last paragraph that it's the one who was the daughter of Sir James Schaw of Sauchie
"7. (Sir) James Shaw of Sauchie .. There is a charter in the Register of the Great Seal to Marjory Kirkcaldy, spouse of James Shaw of Sauchie in liferent, and to James Shaw, her son and heir apparent, heritably of the lands of Coldoun, Cavilstoun, and Brunthill, in the shire of Kinross, on resignation by the said James Shaw of Sauchie, dated 2 May, 1558. (Ibid. Lib. 31, No. 421.) James Shaw of Sauchie had a charter from James VI. to himself and Marjory Kirkcaldy, his spouse, in liferent, and to James Shaw, their son, in fee of the barony of Sauchy, elated Apud Castrum de Stirling, 4 August, 1578. (Ibid, Lib. 35, No. 548, and Lib. 36, No, 586, and Writs of Sauchie.) John Shaw, son lawful to ane right honourable man, SirJames Shaw of Sauchy, knight, is named in 1582. (Writs of Sauchie.) " Will Shaw, Master of the Wark, is cal'd brother to John Shaw of Broiche in 1582, in a charter to him by James Shaw, appearand of Sauchy." (Ibid.) [Crawfurd, in his Notes of Sauchie Writs, says it was this Sir James's daughter who was the king's mistress [query, Sir Alexander]. Elizabeth Shaw had several children by the King James V., the " Gude man of Ballengeich." 1 532, a son was born [see Treasurer's Accounts, April 2, 1532]. This son was afterwards James, Abbot of Melrose, his Tutor, the famous George Buchannan. Abbot James died 1 558.] (Lord Cathcart.)" https://archive.org/details/anent1884/page/111/mode/1up pp109-111
ie Elizabeth Shaw, Countess of Crawford