I asked some colleagues from the Azure team to weigh in if I got anything wrong, but I believe the x-pack questions are answered here: GitHub - elastic/azure-marketplace: Elasticsearch Azure Marketplace offering + ARM template
The TLDR is that for 6.3+ x-pack is always bundled but there is a param (xpackPlugins) to switch between the basic version and the trial/commercial version. Before 6.3 there is an option to bundle without x-pack (same param) and a few options to get the license you want if you do install it.
Is there a managed elk or elasticsearch service ? by managed service I mean a service with SLA garanteed by elastic.
Not currently on Azure, though we are working on that (no ETA yet). For AWS and GCP, there is the Elasticsearch Service cloud offering with various SLAs/etc - it is described here: Official Elasticsearch Pricing: Elastic Cloud, Managed Elasticsearch | Elastic
Alex