Which browser has the most compatability with todist?
I should say I'm on a mac.
Todoist will work flawlessly on any browser that can handle HTML5 which includes pretty much any modern browser (Safari, Firefox, Chrome). The only compatibility issues can be seen in older versions of Internet Explorer, but this issue should not apply to you.
Does that apply to the gmail plugin?
In most cases - yes. It should work correctly at least in Firefox and Chrome. Please try it out and if you'll experience any issues - let us know what browser did you use.