Due to lag and other issues, online racing won't have the same grip as offline racing. For this reason, if you plan on practicing for an event or league race it is best to start your own dedicated server and practice there as this will give you the best chance of having a good setup for the race.
For best results, setup the dedicated server to where you are practicing in practice 2. Once setup, you can join with the LAN option as you don't need to make your dedicated server available to the internet, just to LAN.
The down side to this is that in order to practice with mods, you have to have the mods installed in both the dedicated server as well as your Race 07 directory. If this is not acceptable, then practice online as you will be getting the exact environment that you are going to experience when you join the race server on race day.