Can I only configure a total of 16 HSRP VLAN interfaces or 16 HSRP processes in the Supervisor Engine 2-based system?

아니요. You can use the 16 unique group IDs on as many interfaces as you like. 16 HSRP groups does not mean that you can have only 16 HSRP processes or 16 VLAN interfaces with HSRP enabled. The only caveat is that you can only define up to 16 HSRP processes per interface. 하지만, it is very unlikely that you would need more than 16 HSRP processes per interface in a well-designed network.