Logical Architecture of SharePoint

I have a requirement to implement an Enterprise portal in SP 2013.
The total number of users are 5000 and out of this 5K users, 500 are concurrent users.
they will access my site and perform document upload and take part in discussions.
So, all in all its a collaboration portal where people will communicate through Site Mailboxes functionality and discussion forums.
For this, I am told to draw a logical architecture diagram.
Am confused with how many site collections need to be created,how many sub sites etc.

1. it would be great, if anyone can provide with any sample SP 2013 OR SP 2010 logical architecture diagrams.such that i can get an idea how to draw logical.arch.dgrm based on my scenario.

2. I have Visio 2010 installed on my machine, but I don’t know which stencil should be used to represent the logical architecture diagram. Which one should I use?