I know the answer you seek. :)

LITE version is basically just a model replacement, no need to use pre-made Empire for this.
With normal version you have to use pre-made Empire (however you can edit it and save in any way you want) and that will give you a new tech on start of new game (not sure if on loading old save) that gives you access to special classes (above destroyer).
New classes are pretty balanced against vanilla and doesnt affect any other aspect of the game. Though Id suggest to play with ISB as it enhances gameplay dramatically.
Also, no weapons are added by this mod, unless you use Turbolaser Weapons mod.

Ok, got ya.

I'm playing with the Empire ship pack (not lite) in my game and apparently unlocked the new classes but they haven't shown up yet. I was thinking I needed to play as the Empire (specifically) to see them.

They unlock with Cruisers, right?

@James009 to get the Ships you need the event tech from the start and then the spaceport tech

Anyway not to have to research the tech for the ships?

@[RG]Jimbob if you are doing it right there is no need to research and lite ships dont get anything except for the replaced models, do not use the LITE with prescripted race

Hello Elratie, So I was using this mod before the latest patch and I was able to edit the empire corvet right when I started (I'm not using the lite version). I have played a bit and have upgreaded a lot and still can't change the corvet class. I have watched XP Gamer and in his video he can edit them right when he start. I was wondering if you could help. Thanks

If he was playing an older version of the game it could be because Corvettes had more hull types before the latest update.

Anyone know if there is a mod that restores that? Those were better times.