Use tabs, not spaces!
Tabs vs spaces are the most ridiculous thing I have ever seen in IT.
There is a famous scene in Silicon Valley, where Richard says his main goal in engineering is do decrease size, so he can't stand how people can use 2 or 4 characters instead of one. It's funny, but probably not exactly valid (compression handles this).
So people keep arguing. "4 is better because indent is more clear". "2 is better because with 4 the code growth horizontally instead vertically", "Bla Bla Bla".
Both 4 and 2 spaces are correct. Everyone is right. Everyone can have some preferences.
It just doesn't matter.
I know why people argue - when I use 4 spaces for a long time, I get used to it and I want to use 4 spaces. Others do the same. And this is the matter of preference, so we can't solve it.
This is why there are tabs
The tab is a single character, but you set its size on your local machine.
If you like 2 spaces, you set in your IDE that tab should be the size of 2 spaces.
If you like 4, you set 4. You can even set 20 if you like. Your choice will not affect others.
How about code reviews?
Indeed browsers (at least Chrome) sets the huge size of the tab which is something about 8 spaces.
Just use some Chrome Extension and you are fine.
Ask good questions
The question wasn't if you should use 2 or 4 spaces or tabs. The question is how to make people comfortable with their code style and how to make their environment local, not affecting others.
I think it's quite simple, but I don't see many people realizing that.