ad 1: werks are just the individual changes that make up the new version. So they are the same no matter how many or what kind of hosts you monitor. That’s why you as the monitoring admin should inspect the incompatible werks and check if they affect your environment. For example, if a werk changed the naming of a services on, say, Fortigate firewalls, then you should do a service rediscovery on your fortigate systems, and perhaps adjust rulesets etc. If you are using only Checkpoint, then this does not affect you. In both cases, you can then acknowledge the incompatible werk in question to indicate you have checked it.
ad 2: yes, if the werk is compatible, then you no action is required. You still might want to have a quick glance at the werk subjects so you know which bugs are fixed etc.