For the vCenter part, you must choose the platform (physical or virtual), the operating system (Windows-based or the appliance version), the amount of the resources, and the type of deployment (embedded or external PSC), as will be discussed in Chapter 4, Deployment Workflow and Component Installation.
Note that some deploy topologies have been deprecated, so be sure to read the KB article 2147672—Supported and deprecated topologies for VMware vSphere 6.5 (https://kb.vmware.com/kb/2147672) in order to choose the right deployment type.
Starting with vSphere 6.5, VMware recommends the usage of the vCenter Server vCSA option, with an embedded deployment (good enough for a small environment) or external PSC (if you have multiple vCenter servers and you want to use the Linked Mode feature across them).
The debate between physical and virtual remains old school, considering that almost all deployments have virtual vCenter components, but VMware still supports (though perhaps it will not, in the future) a physical installation.
Be sure to use dedicated systems for vCenter components, just because there are so many ports that are used and you can only change a few of them (anyway, avoid changing the default ports to simplify future management and troubleshooting).
Also remember that both the PSC and the vCenter Server have several dependencies both upstream and downstream (as discussed previously); be sure to analyze all of them before designing your solution, in order to understand the impact of the lack of vCenter services. More information will be provided in Chapter 13, Advanced Availability in vSphere 6.5.
There are also some good resources for vCenter design called vCenter Server 6.5 Light Board Videos, available at https://blogs.vmware.com/vsphere/2017/08/vcenter-server-6-5-light-board-videos.html