Hello everyone.
I am only flying for 6 years but I am basing this on a few years' research at the flight academy.

Using thumbs and fingers is a better way to control your plane for the following:

each finger (index of thumb) is responsible for different movements of the stick.
for example - on the elevator/aileron stick (mode 1),
the index finger is responsible for pulling (up) and rolling to the right
while the thumb is pushing (down) and rolling to the left.
try doing each of those separately or even better, try to do the opposite movement
with each finger and feel the difference for yourself.just to get the idea of how much accuracy you are losing by using only the thumbs.
And since it is more comfortable to take the sticks out (for example knife edge by rolling to the right and applying left rudder), which is the common way to do, you get better control on your plane.
This way you don't apply too much pressure on the sticks and can move them around a lot smoother.
As for speed - you should fix the expos and not less important the sticks height to your convenience to get best results.

I found out that most "old school" pilots use thumbs only, although the do agree that using both fingers is better (old dog, new tricks...).
As for me, I use both fingers and no tray!

I hope I passed the idea right, anyway, it is based on research.

Best of flying to all, TOs and TFFs.

Gabi