In 5G NSA, NR to NR handover means LTE MCG releases 1 SCG and adds another SCG right?
Or is there a defined handover process through LTE MCG?
Yes, NR to NR handover is SCH release and addition.
While keeping LTE cell unchanged.
When changing LTE cell, NR is automatically released.
Yes. In NSA there is no Handover between NR. There is SCG1 removal and SCG2 add.
Handover is the process of changing the PCell (in case of DC, the PCell of the MCG)