Yeah that pretty much sums it up. At the end you simply have try it. If it runs smootly depends on how powerfull the CPU is as well as the GPU and the amount of memory both have. And of course how many things are running on the background.
Than it also depends on the maps themselves. If the maps have a high Extreme End count as far as textures than the computer needs to work harder, if it has less than the drain is also less. And it also depends on the total amount of textures. For all those reasons its difficult to predict what happens.
And the specification i give are only very general guideline. But seeing your specifics i asume it will run fine as i could run them also with a 256 card(on a desktop system). But indeed, at the end you will only know when you try it

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