As far as I've read, PWM shouldn't be a problem, at least with the S14 Flip. PWM is most commonly reported on the Vivobook with OLED display (but it doesn't seem to be a problem there either), and since the S14 Flip doesn't have OLED, it shouldn't be a topic here either.
It is possible to increase the memory up to a maximum of 24GB. Here's the compatible strip:
Crucial Laptop Memory (1 x 16GB, 3200 MHz, DDR4 RAM, SO-DIMM)
For more or less recent AAA games, you will probably have to set the graphics to low/medium in order to maintain a decent framerate. We recommend that you consult benchmarks to get a better idea of rendering.