Every county is different with how they deploy their officers. It will depend on time of day, staffing shortage etc
As for what you experienced, a police car will activate lights when it wishes to exceed speed limits. For the vehicle to be doing 110 without lights then its breaking the law.
Types of unmarked vehicles again vary from force to force. Mainly they are diesel now for budget reasons. Down south we use 535d, 335d. Then a host of other vehicles.
How do I know? It's my job
