here use this site if mother board doesn't support it tells you :
http://www.userbenchmark.com/PCBuilder
for PSU : coolermaster.com/power-supply-calculator/
what you say is normal lag not an unusual lag, and that,s because of integrated graphic they are not made for gaming (your laptop), set the setting on med and if its not fixed set it on low, also lower the resolution if non of that helped
http://gpu.userbenchmark.com/Compare/Nvidia-GTX-1060-6GB-vs-AMD-RX-580/3639vs3923
http://gpu.userbenchmark.com/Compare/Nvidia-GTX-1060-6GB-vs-AMD-RX-570/3639vs3924
my rec : go for 1060 6gb
PSU is fine but to make sure use this : http://www.coolermaster.com/power-supply-calculator/
and i think 1060 6GB is what your looking for : Nvidia GTX 1060-6GB
get one with good cooler and if you want to spend less get Nvidia GTX 1060-3GB
this is the benchmark...
your graphic card is not good for gaming , turn down the resolution of the game that might help
set it at lowest one and see if there is steel lagging or not