I've had this lag happen in the past if the drive I was right clicking had spun down due to lack of activity and had to spin back up.
However, I would recommend checking your drives with CrystalDiskInfo and see if there is any lag selecting discs using that.
Also, have you tried updating Intel Rapid Storage Technology to a newer version? Try using 14.8.16.1063 (I use it with my Z87 motherboard).
And I would also recommend updating to Windows 10 1909, 1803 is no longer supported by Microsoft.