...
In TH I could spot the word just once being mentioned to refer to the
Wood-elves (but I don't think that is very meaningful):
The feasting people were Wood-elves, of course. These are not wicked folk. If they have a fault it is distrust of strangers. Though their magic was strong, even in those days they were wary. They differed from the High Elves of the West, and were more dangerous and less wise. For most of them (together with their scattered relations in the hills and mountains) were descended from the ancient tribes that never went to Faerie in the West.
Reading too much into statements in TH for the "serious" legendarium is probably always very iffy. Some doubtful branches of psychoanalysis claiming descent from Sigmund F. of Vienna do like to indulge in such things, but they impress me as straying a bit at least into esoteric territory.
That said, our overall impression may be a bit skewed towards the
Light-Elves and the
Sindar or
Grey-Elves who came in contact with them. Only east of the
Misty Mountains are we told of
Silvan Elves, in both
Thranduil's
realm and in
Lothlórien. In both cases, it is not unreasonable to assume a certain "civilizing" effect on the Silvan Elves, making them a special branch of the "Moriquendi" or Dark-Elves, or even the "Avari" or Unwilling. There could quite possibly have been
Elves, in contrast to the statement in TH above, who were "wicked folk". Eöl, his son Maeglin, or Saeros of
Doriath do point in this direction. Or for that matter, even the High Prince of the
Noldor Fëanor had some decided character / socialization defects. So perhaps some of those "Avari", the wilder ones, who never got beyond "tribal" organization, could have been more fitting "material" for
Melkor to wreak his corruption on. Perhaps they also were already somewhat ugly, a concept which runs contrary to every real-world tradition of Elves being "fair folk" if dangerous to mortals. But those traditions do seem to spread the physical characteristic of Elves more widely than what we know from JRRT's writings.
The
Orcs had been introduced into his (early) legendarium as an (enemy) "infantry of
the old war about whom one must have no compunction" about slaughtering them in masses. JRRT had no end of trouble reconciling this offhand use of Orcs with his own beliefs, and never finally managed to reconcile their variously being considered "low-level
Maia" (for the early Orcs) to Elves to
Men to "upgraded beasts", or any cross-breeding among all of these.
But tribal-level wild Elves leading to
Orc tribes - not entirely inconceivable.