yes. keep in mind that how metadata/special vdevs work is that your index for your storage drives (like the table of contents) get added to it, which can speed up things when yo have say 1000s of folders with 1000s of folders in them. They also store all the files below a certain size (can be changed via truenas interface)
Also apps created via the hexos interface work exactly the same if created through the truenas interface
the way to check would be to run some shell commands in the truenas interface, you would get an output like this
steps to check
1) enter truenas interface
2)enter the systems tab on the bottom left
3) enter shell
4) type "sudo zpool iostat -v <name of pool>"
5) itll ask for a password, your keystrokes don't show as a security feature
5) add a bunch of small files to your pool
6) run the command again and check if the special vdev increased in size.