Asking advise about window tinting is IMHO the same as asking about what to wear for cloths. Think about that.
*I support Law Enforcement "BLUES" in every aspect so I must at least say that you should consider the vehicle codes in the place you live. If you do get red lighted by any law enforcement roll down all your windows and if at night turn on your interior lights as well so the officer(s) can CLEARLY see the inside and all passengers.
Common sence can go a long ways when thinking about tinting? Is it for looks or function. The type of tint available now, clear UV is the same UV protect as darker tints.
The interior color will have effect on what the outside looks like.
I live in California, all my vehicles have always had dark tints and since the the late 70's I have never gotten a citation for the *tints.
I would suggest to go with what you want just keep in mind the biggest factor of cost should you do get a citation for having tinted window that do not comply.
Oh I do believe that in all states including Canada that even if you do comply with what qualifies as legal an officer still can cite you for what he/she feel is a safety issue and in court it could stick!
M3 has 2% all windows and 35% drivers and passenger front and UV clear on the windshield.
But as you can see with the black exterior and black interior the front windows look like 2% at som eangles.
Pictures just taken .7:00a.m 52f
View attachment 243802
I forgot to note that in some cities in California (mostly LA) the local police DO IN FACT carry a device to measure the window tint.

The CHP (California Highway Patrol) does not by policy.