There's a lot of changes to take in, the mod is nothing like ELS V6
As far as car modders is concerned:
There's no change in how ELS works for you from V6 to V7, you still need to set up the models the same way, however you can now have secondary lights set up in a rotating pattern as illustrated in the ELS guide.
As far as normal users are concerned:
All ELS V6 models are compatible with ELS V7.
ELS HAS been extensively tested, if it doesn't work for you, then you have made a mistake somewhere in your setup.
You now have to customize a bit more than before:
You do not have to use the default_config file, you can create a copy of the default config file and rename it to whatever you want as long as you remember to update ELS.ini with the new name.
The config file system allows you to extensively customize each vehicle slot, you can create a different vehicle config file for each car model (one for police, police2, polpatrot, pstockade, nstockade, noose, fbi and so on) or you can use the same config file, all you have to do is update the name listed under the vehicle slot in els.ini.
It may be a lot to get used to, take your time and learn how it works, I didn't learn it overnight, I had to figure out a lot of it myself with only a brief introduction from Caine. It's not impossible to learn by doing, ELS is fine, it is not released broken in any way, if your game crashes or if it otherwise doesn't work it is because you made a mistake, use the guide and go though your settings and troubleshoot.