@TommyB1972
"Is is best practice to also have running VM's on the VSAN host?"
I am not really sure what the point of having hosts at all would be if you were not going to run VMs on them!
"How much data loss will i have when a ESXi host in location A goes down."
So the main point of 2-node clusters (and vSAN in general for the most part) is that data has some redundancy and is not lost when a single node/disk/Disk-Group becomes unavailable - think of it as RAID1 across nodes, with a replica of all data stored on each node and small metadata stored on the witness (only used as a tie-breaker). Thus if you have standard FTT=1 Storage Policy applied to the data then no data will be lost.
"Will the data replication between the 2 vSan nodes be synchronized a a-synchonized?"
Synchronous - IOs are not committed until cache-tier on both nodes writes the data and acks.
"Where do i place the witness node?"
Anywhere really (except on the data-nodes) - this doesn't have beefy hardware nor low-latency network requirements, typically vSAN customers run these in the cloud or on some other VMFS/vSAN infrastructure.
