No worries
Don't panic.
Yes, liquid detergent can leave a residue if used in to big or small quantities, but that is the same with every detergent and softner.
Yes, powder would be my choice, but liquid will work just as well as long as used correctly.
Just go ahead and use what you like from now on.
My motto with that: Manufactueres of detergent know detergent, and mechanics know the machine, not vise versa.
Follow detergent manufactueres advice with a hint of common sense (if you notice the laundry dosen't smell fresh and clean, use more detergents, warmer water or extra rinses; if you notice detergent residue, to much suds or such, reduce dose or add rinses; if your load is big and soiled, used more, if its small and less soiled, use less).