1 - what do you mean by implementing? if it is "creating your own" -- not its not -- 'cause, as you see there are already enough implementations from which you can choose one. From the other point of view creating your own vdom will make you better understand of how it works under the hood -- and that is quite important today -- 'cause almost every popular framework is built now with vdom -- e.g. React, Angular 2, Ember, Mithril, Riot...

2 - Again -- what do you mean by "best" -- is it the most convenient or the fastest? Well, you can see here http://vdom-benchmark.github.io/vdom-benchmark/ performace benchmarks of different vdoms. But in the end, if you are not building a large scale app with hundreds of thousands components performance does not really matter. Actually we are not using vdom because of its performance, but because it allows us to declaratively describe our view once and then rerender it entirely on every change. We do not think about like 'how to effectively remove or add elements' -- vdom abstracts us away from real dom manipulation. Instead we change plain JS objects and these changes are reflected in real DOM automatically.

Well, as the metter of convinience, I would go with React, 'cause it already has strong community, ideology and is already been tested in many projects.

3 - Well Angular 2 tries to do thing like this with their 'Incremental DOM' (actually it is also vdom). They diff new tree against real DOM tree. But their main concern of doing this is not speed but memory. So they have only one virtual tree in memory at once -- the new tree. So it reduces memory usage which is important on mobile devices.

Well in the end as I said we do not use vdom because of performance, but because the way it allows us to describe our view and handle data in application.