I'd ask what exactly the model name of the CPU is, also don't forget to ask about the amount of RAM and its speed.
The graphics card will give you ~90fps on Very High according to Tom's Hardware, which is still more than enough, but the seller isn't being entirely honest. Not a big deal, though.
Keep in mind that script mod usage such as the usage of LSPDFR and its associated plugins is CPU intensive, not GPU intensive.
I have a GTX 1060 6GB which gives me over 100fps on Very High in vanilla, but this drops down to 30-40 due to the amount of mods I have because of my CPU.