I think this is probably Roger Zelazny's Changeling (1980).
Two young boys are switched between a magical world and a technological one, and grow up favouring the system of their birthworlds, making them outcasts. Pol, the magical one, sees magic as strands. Quoting from the plot summary on Wikipedia:
In the world of magic, the young Mark Marakson is obsessed with devices, building water wheels and later, steam engines. He does not understand why the people on the farms and villages rely on magicians rather than using the machinery he creates. Young Pol, meanwhile, grows up a poet, musician and singer, marked by the white streak in his dark hair. He is a great disappointment to the man he regards as his father, who is an engineer. From time to time he sees glowing strands in the air which he can touch to make things happen.
Mark is ostracised by the people around him and wanders in the hills until he finds a graveyard of machines, left from the ancient war between magic and technology. Able to restart them, he returns in triumph on a flying machine to claim his childhood sweetheart in the village, only to be assaulted by the villagers, losing an eye. Fleeing back to the graveyard he creates an army of machines to take revenge.
Mor, realizing that he has disturbed the balance of the world, goes to retrieve Pol to counter Mark, revealing Pol's heritage and powers to him. To return Pol, the elderly Mor has to remain in the technology world to balance out the transfer. He dies in a park where every tree, bird and insect is artificial.
There is a sequel Madwand (1981), but it's mostly about Pol finding his place in the magical world. (And a sentient curse that likes the colour green.) If you recall the name "Belphanior" you might have read the 1989 omnibus Wizard World which contains both novels.