Hi Slicepong, Your tight it is very effective of you can hit a topspin with less arc and more power, I wouldn’t say its really a flat shot as such but as you mentioned brushing over and through the top of the ball rather than too much brushing upwards is definitely the way to do it. Also like you said it’s about picking the right time to do these, like avoiding it on backspin or if the ball has dropped too low but if you can pick the right time to use it for sure it’s a great shot.
By the sounds of it I would say you can keep practising this but even on your slower and more controlled topspin shots try to improve and work on your bat acceleration through the ball to get more spin and zip through the table. Also your spot on if you are brushing the top of the ball more without enough acceleration it won’t be an effective shot or will go into the net. So keep going with practising these shots and focus on acceleration through the contact area and top of the bounce timing with a smooth but quick action!