It's always difficult to say whether you will be able to transition into classical authors "with ease," but I'd say that the LL2 vocabulary is pretty comprehensive. In fact, I think a lot of people struggle through the latter parts of it because there is a lot of new vocabulary every chapter (compared to LL1, which is better at repeating core vocabulary frequently).
By the end of LL2 you should be able to read some of the standard classical authors (Livy, Cicero, Caesar...) without major issues. I think most of Orberg's modifications are grammatical in nature.
Horae quidem cedunt et dies et menses et anni, nec praeteritum tempus umquam revertitur nec quid sequatur sciri potest. Quod cuique temporis ad vivendum datur, eo debet esse contentus. --Cicero, De Senectute