I haven't played (nor bought) the
RPG expansion yet, so for now I can only go off of Modiphius's various statements on Facebook and of course their development blog (
https://www.modiphius.com/development-blog.html). The
RPG expansion, while building on the rules of Wasteland Warfare, is a self-contained
RPG that from a wargamer's perspective offers an additional way of using your miniatures and allows you to use somewhat customized unit profiles in the wargame in addition to the normal unit cards, offering even mor customization.
The
RPG expansion does not require anything from the wargame except the dice, so provided you have a set of those (though two are more convenient) you can play the
RPG by itself.
As said I haven't played the
RPG yet, but I have played the wargame which is a flexible ruleset with elegant rules and nuanced dice mechanics that allows you to play anything from straight up dudes punching each other to
RPG-lite with event decks, loot mechanics, skill tests for climbing, lockpicking, hacking and spotting/perception, possibly a few more. Based on that and going by what's been posted on the blog, I'm tempted to say the expansion is a true
RPG.
Since it's based on the wargame, and meant to be expanded as the wargame gets new unit and equipment cards, you are currently limited to Brotherhood of Steel, Super Mutant and a variety of Survivor rules, with Raiders coming up in the next couple of months, Institute planned for the end of the year, although Modiphius tends to be a little late quite often, and Enclave after that. You have a variety of robots and creatures covered already, and these will also get additional profiles this year. As such, you are somewhat limited to the speed at which Modiphius produces models and thus unit cards to go along with them, and the system is card based rather than sourcebook based as conventional
RPGs are.
From the blog posts it sounds like the rules of the
RPG are somewhat flexible about whether you wish to use miniatures or not, which makes me think that if you want to have combat happen in abstracted instead of miniature form, that should be possible.
Edit: Also, Modiphius has announced a 2D20
RPG system for Fallout for next year, if that is more to your liking.