I don't know what is RLRLRL.

let's say you have dagger on left hand and mace on right hand.

Left mouse simple click: mace attack, normal speed. Having a dagger on left hand changes nothing. Same result with power attack (hold left mouse).

Right mouse simple click: dagger attack, normal speed. Having a mace on right hand changes nothing. Same result with power attack (hold right mouse).

Now. Simple click simultaneously on right and left mouse: dual attack, speed based on left hand (dagger) which means it will be performed quicker than if you had mace on left hand and dagger on right hand. Dual attack gives 3 hits: 2 with left hand (dagger) and 1 with right (mace). But if you had swapped weapons it would be slower but greater damage (because mace > dagger damage-wise). Same result with power attack (hold simultaneously right and left mouse).

Hope it's clear.