Does the lag occur when you play with the laptop plugged into the wall? Or only when playing on battery? Also, do you have energy saving mode enabled?
Can you please either post here or e-mail to buru@buruthebull.com the log file? You can find it here if you use the Itch Desktop App: C:\Users\<YOURUSERNAMEHERE>\AppData\Roaming\itch\apps\rivencliff-sunbath\RivencliffSunbath
Or just inside the folder where you extracted the game files if you downloaded the .zip file.