“Which class” threads are impossible to answer, unless they are very specific. The reason is that your preference for a playstyle overshadows EVERYTHING else. By miles. And you don’t know which playstyle you prefer until you try them.
Regardless of class, I will recommend that you choose one of the dominant servers - Draenor, Tarren Mill, Kazzak for Horde, or Silvermoon or Ravencrest for Alliance. See https://www.wowprogress.com/realms/rank/eu/lang.en
Every class has a DPS spec.
Nobody knows what gameplay will be engaging to you.
Every class can make impactful choices.
When it comes to a healer’s toolkit, of the four you mention, I think I’m safe in saying Resto Shaman has the biggest toolkit. Against that, Monk and Druid also have the option to tank, which is perfect for soloing hard world content. OTOH, I see Shamans with their Elementals pwning rare-elites in the current Elite zone Forbidden Reach, so they do pretty well.
The best advice I can ever give a new player asking “What class” is to look up gameplay of that class on YouTube, and see what appeals to you. It;s the nearest you will get without actually playing it.
If you have a Free Trial Boost, you can take each of the classes out, but Free Trials are not allowed to use them in instances, so truing out a healer that way is useless.
