I mostly just switch keyboards in conjonction with the macOS virtual keyboard. Writing in French is more than just about quotes for example. Dictionary and spelling correction are bigger issues in my opinion.
I'm kind of old school. I deactivate all "smart" features. I remember typing in French on an American QWERTY physical keyboard configured as "Canadian French" decades ago. You know, fingers memory? This was well before Unicode. Now if you introduce Greek, Cyrillic and Far East...
This can become a complex thing. Just think about printing and system portability. Even just in Canada there are more than one standard keyboard layout for both English and French!
For casual communications within Canada using "English" quotes is not a big issue. Working for government is another story 😉.
Hope that helps,
WD