Should I use the L2 plugin as a limiter before or after rendering a project?I mean,which would be better for the project to run nicely?
Always run it as the very last plugin in the chain.
Even if you are going to be sending the mix away for mastering, setting both threshold & out ceiling to -0.3 will just prevent overs.
If even at those settings it's too hot, then pull back the entire mix earlier in the chain.
If levels are too low, you can use it to lift the overall levels, but I wouldn't. I'd compensate earlier in the workflow.
If you're attempting to do the mastering yourself, then there are two ways to go.
Mix & master all in one.
These days there's no real loss if you have to come back to the project to remaster later, it's all saved & can be restored in a few seconds.
Mix first, master later.
I'd still use it to just hold any slight overs. Then come back later & use it on the final stereo mix to do your mastering.