#3 All tea comes from the same plant so theres not much difference between teas actually. But they have still some differences in benefits like white tea is more calming and black tea has normally more caffaine (wich can be both good and bad).
But Matcha is a step better than other, since you'll get all of the tea leaf in a cup instead of just whats steeped out.
For me it's really the 'enjoyment' and all the happy emotions that come with the simple experience of tea. I think this mental benefit is a health benefit in itself.
With regards to the scientific health benefits, I think research these days is too much focused on what's good and bad. It should more look in to which tea is good for 'who'. Really, every individual is different. Some 'cooling teas' are better for those who're 'heaty'. And those who lack energy and have cold hands and feet should go for a more 'warming tea'.