I have many biplanes and fly them all the time.

Most RC model biplanes design around some of the potential problems.

The increased roll rate is not due to less inertia, but rather that you have more operating control surfaces. Normally the surface movement has to be toned down GREATLY to prevent over-responsiveness. Case in point the Ultimate the OP posted about needs only 4-5mm of aileron movement for HIGH RATES.

They are not inherently less efficient, quite the opposite, the biplane design was utilized to increase lift efficiency and structural strength for a given weight... the reason the Wright brothers never went with a Monoplane.

They sometimes seem to come in hotter, not because of inefficiencies, but rather the larger frontal cross section causes them to slow down VERY quickly when the throttle is chopped. In effect they are more draggy.

However certain designs such as the Skybolt, make the wings slightly wider to further increase lift, and let the plane decend far more slowly.

Often the characteristics of short tailed, short winged BiPlanes such as a Pitts, are used to describe general characteristics for all biplanes.
This is a mistake and is often repeated. A Pitts Biplane is designed for aerobatics and great snap roll behaviour. As such it has short wings and a short tail. You can apply Beau0090_99's observation to a Pitts Biplane.

However this is erroneous for say a Skybolt or a Stearman. Just try to drop a wing on either.

And then there are the high lift Biplanes like the Tiger Moth.... which you can land at a walk.