Upgrading from 100 to 200 amp load centre with 100 amp service shutoff
You can use a 200 A panel with 100 A service with no problem; it's done quite regularly. You can just put a 100 A main breaker on it (saving the 200 A one it may have come with for later). A lot of times the 200 A panels are cheaper, have more slots, and/or are just physically bigger (easier to work in), which is why they are used even if the service is less than 200 A.