Razer Blade 15 base(mid-2019) fan issue

Recently I bought my first RB15 Base and I have some question about system fan

first of all I'm not from english country, It could be some error with my English..

1. When I started to using it with power plugged, the fan being louder than unplugged, I didn't do anything on laptop It's on idle condition. I hope it could be silenced like unplugged. any idea?

2. After finish playing game like PUBG/COD:WZ the fan is still running crazy about 10 minutes and it goes quieter than before, but it is also loud.. (Synapse setting : balance / fan : auto) I think it's abnormal

3. is any USB powered device (mouse / keyboard / etc..) effect on fan control?

4. Can I figure it out why fan running like crazy and reason of running? how can I know current RPM of my fan?

I undervolted my CPU -0.100 to -0.140

If anyone give a comments, It could be helpful.. Thank you for reading