Would it be possible for ANY of the fae (Logan, Remus, Linda, Percy, Bella etc) to be able to become like Virgil's mother if they lived long enough? Or does being born close to a solstice change some things?
yes! any fae who lived long enough, even one who was born very late
it's like... birth time of year is like starting stats, and then age + maturity play a secondary factor in the given fae getting stronger as time goes on.
so Logan was a very early Spring, but he was still not very powerful as a baby, because he was... a baby.
He matured very quickly for a fae, and therefore also grew into that power MUCH faster that an early spring green man typically would.
Logan, at twenty-one in Seelie, is insanely young chronologically by fae standards (Bell at twenty would have pinged to a human as around eight or nine, in comparison) - but because he's already matured into adulthood, his magic matured along with him. as an adult, his magic will only continue to get stronger, even when he stops aging.
The exceptions to this "not super powerful as babies" rule are Virgil, Durant, and Linda, as they were very deliberately constructed in such away that they were born already insanely powerful, especially Virgil. For Virgil, this was because Mother made him for the specific purpose of serving as her deputy and Lord of the Forest. Durant was similar, being designed to be Virgil's deputy.
for Linda it was basically "well i have to give my son a sturdy baby."