When using the vCenter 6 appliance as an Autodeploy server you can also use the appliance as your TFTP-server. But for that to work you need to start that service and enable access to it via a firewall rule.

Of course you also need to enable the Autodeploy service itself, which can be done from the vSphere Web Client under Home - Administration - Deployment - System Configuration - Services. 

One of the topics in the VMware vSphere Optimize and Scale course is how the amount of RAM is calculated that your host should have available as a minimum before processes such as ballooning and swapping become active.

The course material provides this table that shows us how this minimal free memory is calculated:

With this simple script you can get and set the ESXi thumbprint on the vSphere Management Assistant. This is necessary starting with vSphere 6, also explained in this knowledge base article: KB2108416

When sizing virtual machines you should be aware of the number of physical cores available in your ESXi-host and whether or not it has Hyper-Threading enabled. If you blindly follow the number of vCPU's you can add that VMware presents to you, then you could end up with VM's that offer poor performance. If you want to understand Hyper-Threading and why this is important for sizing please read the articles that I have listed at the bottom of this page.