If using push pins heatsink from intel's heatsink, be sure they are all pressed down all the way to make sure the heatsink are actually touching the CPU.
Resetting motherboard settings to defaults are always ok as it can go to motherboard settings again if needed, do take some notes on what settings are getting changed when resetting to defaults. Default settings could sometimes make windows fails to start, so going back to motherboard settings to change between AHCI/Raid/Legacy, or boot order, or UEFI option, may get windows to start again. Some settings like CPU voltage and speed changed from default may have a possible cause of the slowdown problem.
Resetting motherboard settings to defaults are always ok as it can go to motherboard settings again if needed, do take some notes on what settings are getting changed when resetting to defaults. Default settings could sometimes make windows fails to start, so going back to motherboard settings to change between AHCI/Raid/Legacy, or boot order, or UEFI option, may get windows to start again. Some settings like CPU voltage and speed changed from default may have a possible cause of the slowdown problem.