I guess that no entry in the .vmx file simply defaults to the pre-defined virtual adpater type for the selected guest OS.
To configure a specific adapter type you may modify (or add if not already present) "ethernet#.virtualDev=".
Common possible values are "e1000", "e1000e", "vmxnet3"

You can find out about the differences in e.g. https://rickardnobel.se/vmxnet3-vs-e1000e-and-e1000-part-1/

André