Hello again people , some more dumb questions for you ?

As previously stated in "gear" re: weatherproof DSLR's , I have pretty much decided to go down the Canon 7D mkii path.
[And then I 'discover' the 70D , apparently much better for video with its articulated LCD screen and "touch screen follow focus etc". But this is another story....]

Question: Is the 100-400 mkii lens FULLY compatible with the 7Dmkii ? I have tried to find a definitive answer to this question in innumerable forums , only to be more confused than when I started. Various 'stories' of focus problems , limited focus points , locking-on to subjects etc etc.

Does the 7Dmkii and the 100-400 lens retain all functions when used with a 1.4 TC [mkiii version?]

Will I have to 'calibrate' the focus of the lens/camera to use it for bird photography?

Better off with a straight 400mm f5.6 lens?

Much thanks in advance for any advice/help ,

Barney.