Handling/Vehicle Meta Lines Help

So me and my buds are new to setting up a reborn server. Can meta and handling lines/files be placed server side or is on the individual to do it client side? How does one go about this? Additionally, are custom sirens possible?

Let’s start off with a welcome! Next time, using the search function on the forums would have probably found most answers.

No, handling and/or meta files can only be added serversided for add-on models.
Yes, if you want to modify handling lines/meta files you would have to add them clientsided.

Searching through the forums will get you to most answers. You might also want to read this topic;

Recent Update + Some information

Read above statement.