"Probably setting the MPAII to +4 and using the ADC level in mudita24 to keep the 1010 from clipping will give best results, but it would not hurt to try -10 also with the ADC level higher. Let your ears and meters judge."
There is no actual analog volume control on the 1010LT's RCA inputs, it's just doing multiplication on the captured signal after the ADC. If you are clipping the input turning the volume down in the software interface just gives you a scaled down version of the clipped signal.
It is better to monitor the actual numbers coming off of the ADC chip. That way 0 dbFS on your meter in Ardour or whatever is actually 0dbFS at the ADC.
In Envy24 control that means setting the 'analog volume' slider to 127, that's where you are actually seeing what's coming off the chip. Above that and the captured signal is being scaled up and below that the captured signal is being scaled down. Control your input level in the analog world before you hit the card. Shoot for peaks around -12dbFS.
Also: there are jumpers on the card itself, you can use the XLR inputs as line level balanced ins. In my experience that's the best fidelity you can get with this card.