Culturally I would say Legolas is one of the
Tawarwaith or Wood-elves, but according to one description, the remigrant Sindar might have brought at least some measure of West-elven culture with them too. A late text (Unfinished Tales) generally notes that these Silvan Teleri had become a small and scattered people, hardly to be distinguished from Avari, but that under Sindarin leadership they
'became again ordered folk and increased in wisdom,' and some learned writing from the Sindar.
This at least seems (to me anyway) to imply that they brought some Beleriandic culture into play, noting the history of Galadriel and Celeborn relates that the Silvan Elves of Lorien became subject to 'Sindarizing' under the impact of Beleriandic culture. Legolas, as the son of a Sinda, was the son of an Elda... by blood he might be fully Sindarin, or not. But what does blood mean regarding this question?
However another late text in
Unfinished Tales notes Oropher and folk:
'wished indeed to become Silvan folk and to return, as they said, to the simple life natural to the Elves before the invitation of the Valar had disturbed it.'
As I said above, however Legolas had Sindarin blood (at least in part) in any case, but admittedly I'm not really
sure what that alone might mean as far as being accounted an Elda or not -- in
The Lord of the Rings the Eldar are the West-elves while the Silvans of Lorien and Mirkwood are the East-elves -- and in my opinion Legolas did not himself live in Beleriand at least, about as West as one could go without sailing to Aman.
It's possible (though I've no text to support it) that the 'definition' of
Eldar Tolkien later wrote about (taken up into
The Silmarillion by CJRT) was yet another internal distinction: meaning
Eldar first referred to all Elves (Peoples of the Stars), then to the West-elves, then later to the Marchers (Eldor), whether or not they had reached Beleriand.
I'm not sure Tolkien saw the latter idea as an
internal addition to the use or application of Eldar (rather than forgetting what he had actually published already), but the term seems to have changed a bit internally in any case.
Erm, what was the question again!
