When we restored my grandmother’s old house in the west end, it was really important to us to keep the character intact. I found this guide listing the https://windowtechcanada.ca/best-window-companies-in-toronto/ best window companies in Toronto, and it made a huge difference. Some companies on there specialize in custom frames that match heritage aesthetics while still providing modern insulation. We were able to get custom wood-look vinyl that blended with the exterior and still got triple-glazed performance. They also gave us mock-ups before committing. I’d say avoid the general contractors for this kind of job and go with someone who knows heritage homes.