Usually. Full doubles will not germinate as well others. Indeed some full doubles may not germinate at all. Many will however germinate and often, but not always, result in a good looking plant and flower.

Albert, please explane further what full doubles means I have no idea please. How do I properly harvest marigold seeds?

Double. Said of flowers that have more than the usual number of floral envelopes, particularly of petals; full.

Also see: Double-flowered

In the bottom of the first pic, is what you want to save. Yes, put them in a paper bag. Once completely dry, the good seeds will not be easily bendable. You can tell bad marigold seed pretty easy. They are super flexible.
Remy