I have never seen a thick airfoil on a modern design. typically they are 12%to 10%
for best efficiency -the thinner the better -
as for the engine - what is used makes no difference - 4 stroke /two stroke / electricmotor - it is the prop disc and low speed of same which adds any braking.
An electric using Back EMF is ideal.
The myth of thicker airfoils adding more lift and drag is simply that - a myth.
First - they have less lift
however on heavy models the lift is more constant at different angles of attack.
The old 3D fun fly models are very numb to angles of attack due to the ultra thick foils
they are also very low on wing loadings - if done correctly.
The thick wings allowed for very light construction due to improved beam loading.
I suspect you will see lighter wing loadings with thinner sections and more relative low speed thrust on future designs.