[Belegorn]

True, the superlatives are there, in abundance. Like in your first quote some of the superlatives given to his brothers are applied to Fëanor as well, "Fëanor was made the mightiest in all parts of body and mind, in valour,... in strength" [Sil, p. 112]

Also applied to him are "beauty" and "understanding", whereas with Finarfin "fairest" and "wise of heart" are used. So one can wonder, how is Fingolfin said to be the strongest of the brothers when Fëanor is said to be "mightiest in all parts of body" as well as in "strength", and "endurance".

Your quote from the note reads to me in this way: "especially Elrond" refers to him, like Galadriel, with conceptions of being able to wield the One, not necessarily Elrond having a better aptitude of wielding it because if you read on you will see them in the same light, apart from Gandalf.

"In any case Elrond or Galadriel would have proceeded in the policy now adopted by Sauron: they would have built up an empire with great and absolutely subservient generals and armies and engines of war, and they could challenge Sauron and destroy him by force. Confrontation of Sauron alone, unaided, self to self was not contemplated. One can imagine the scene in which Gandalf, say, was placed in such a position."

Later on in Letter 246 we are told how the 2 of them rejected the One anyways. It then follows about how in wielding the Ring they would go about taking on Sauron as differing from Gandalf, who alone "might be expected to master him".

Hear me out on this and tell me what you think. Galadriel is interesting because it is said of her in The History of Galadriel and Celeborn; "she grew to be tall beyond the measure even of the women of the Noldor; she was strong of body, mind, and will, a match for both the loremasters and athletes of the Eldar in the days of their youth." [p. 241] What is interesting to me is the part that says, "a match for both the loremasters..." and the inquiries about Galadriel's fighting prowess. It is said she was a staunch defender against her uncle's massacre at Alqualondë. This is basically the only text that I know of her mentioned in actual combat. Now, the text I quoted says she was a match for the loremasters. Interestingly enough a text reads that the loremasters of the Noldor:

"Nor were the 'loremasters' a separate guild of GENTLE SCRIBES, soon burned by the Orks of Angband upon pyres of books. They were mostly even as Fëanor, the greatest, kings, princes and warriors, such AS THE VALIANT CAPTAINS OF GONDOLIN" [The Peoples of Middle-earth, Note 23]

In other words they were not nerds or some such with no aptitude to fight. Rather than being gentle scribes they are "as the valiant captains of Gondolin". Therefore, perhaps it is safe to assume, that Galadriel too was such as these and would probably be able to best Elrond in a sword fight.