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You want 16GB of DDR4 for modern games.
8GB DDR3 was ok up to ~2010, so if you want to play games from back then, it might work.
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Of particular interest are:
Exact make & model of your Power Supply;
Case & cooling parts;
Monitor model & Hz;
Resolution you're running at;
What graphic settings level have you enabled?
it never mentioned that it is ddr3 or ddr4
That's DDR4 if it's from last ~10 years. What game is it?