How to understand all this stack?

Hi, i'm running across all documentation, forum topics, FAQ and i still didn't found usefull high level / overall architecture documentation. The Elastic stack look great. I tried a trial cloud account in order to get log and metrics from other cloud solution like Azure, GCP, heroku and so on.. I learned that i have to use Beats and probably logstach... I was surprised that i have to set up something on my side even if i use elastic cloud as a service. For example, if a want to ingest log from a Cisco router or from GCP, i have to set up a server running logstach ? i also have to set up a server for running filebeat in order to get syslog in my elastic cloud account., it sounds crazy but ...

So now, with all these feature and interaction between products i'm looking for a high level document that explain all this . Specifically, it would be usefull to understand what is Not running and available in Elastic Cloud and what is mandatory to set up in order to make this all working well.
if someone could help me with docs to understand overall hosted cloud solution (not giving link for each part) it would be appreciated.

PS: i'm also looking to find information about using and installing Endpoint Security.
Thank you for your help.
Seb