Hi Nate,
Here are the answers to your questions:
1) Yes, you can create two different clusters and can manage them through vCenter server. The location of the ESXi servers won't matter.
2) Yes, in a same cluster, you can have different model of servers but I would recommend you to use same models in a cluster.
3) You can setup HA (High Availability) on a cluster, which will protect the virtual machine if a host goes down (there are quite a bit of reading needed to understand fully on HA).
Feel free to leave a reply if you got more.
Regards,
Steven.