Fluctuating Hash Rate


I’m new to mining Ergo. I have two mining rigs connected to herominers mining pool.
Rig 1 , 7 x RTX 3060TI non LHR avr. Hash Rate 1.1 GH/s
Rig 2, 3 x RTX 3060TI non LHR avr. Hash Rate 490 MH/s

I am experiencing fuctuation in the Hash Rate. Sometimes Rig 1 has as low a Hash Rate as 400 MH/s. and other times as high as 2.1 GH/s. Why is that? Is that depending on the difficulty? Avr. Hash Rate around 1.1 GH/s which I think is what the GPUs are ment to produce.

But another thing is that Rig 2, with half the Hash Rate has almost delivered the same amount of valid shares. They have been running almost the same amount of hours.

Is my Rig 2, just more efficient than my Rig 1?
Appreciate any comments that can shine some light on this.