I would suggest trying it, I'm not familiar with Votra's cfg so I don't know what it will look like but generally if you want to have better fps you will need to turn down the graphic settings. It just depends on how much graphics you're willing to downgrade and you can always tune it to your liking.
You can use the exec without replacing your autoexec by going into
C:\Program Files (x86)\Steam\steamapps\common\GarrysMod\garrysmod\cfg and making a new file called
Votra.cfg and pasting the contents inside.
It would look something like this:
When you launch gmod, open the console and type
exec Votra
This will make it so you use the settings for this gmod session and you will need to exec it through console every time if you decide to use it. Of course if you like it you can change it into an autoexec by pasting the contents into the autoexec cfg file.
If you run it as autoexec also, you can disable read-only on the file and tweak the settings ingame through the video options so you still automatically run the console commands in there but with some higher graphics of your choosing and then you can play around with it and have some better graphics when you decide