I used to use both Simufly and CS CIVA INS simultaneously.

In long haul flights over the ocean I switch to CS because its no missalign (it isn't real but it is more practical), and follows the heading like a conventional GPS.

And over the land I switch to Simufly INS, previously I have alligned it with the closest VOR after the ocean.

And this way there are 2 navigation systems.

Also I use CS INS to see the distances between waypoints easier than Simufly INS (again is less real but practical)

Simufly CIVA INS is more realistic and more functional (you can load routes via files like real life) than CS INS, but CS INS it is a good addition on both visual and practical level.