As I alluded to in my comment on your post on the Physics SE, Smilei seems to offer everything you're looking for. It's powerful, it's open-source, and you don't need to modify the code in any way - all you need to do is initialize the simulation with whatever parameters you'd like to add and then run the program.
There are three caveats here, though. The first is that although there are several very simple and clear tutorials on how to use Smilei (see here for an example of how to simulate a thermal plasma), the amount of options can be daunting. I would suggest running a few tutorials and then simply adding blocks to those files as needed, rather than trying to write one from scratch yourself.
The second caveat is that, like all plasma simulations, if you want to examine a large or complicated system, you're going to need a lot of computing power. That's just the nature of the beast in computational physics. Running a real 3D simulation is almost always impossible to do without a supercomputer to work with. If you want to use a personal computer, then 1D simulations are a more realistic goal, and 2D simulations are possible as long as you keep the system small.
Lastly, after the simulation has been run, you'll need to analyze it as well. More information about how to do that can be found in the tutorials, but be prepared to spend some time learning some basic plotting and data analysis techniques if you aren't already familiar with them.
