We may not always have that option…

I personally use signal. Never had problems with video calls or anything really.

Lineage and grpahene do different things. Research and find the right for yourself. And instead of lineage you could find a crdroid on if you for example want more customization

Graphene is basically android too. If you install lineage without gapps for example, I think you’ll have great privacy. About the second, I don’t know…