The Janssen (J&J) is non-messenger RNA
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That’s not quite right. J&J does involve mRNA coding for the spike protein. It just adds a step. Namely, it has an adenovirus enter the cell nucleus with a snippet of DNA which causes the mRNA to be produced, and from there the process is the same.
Novavax is fundamentally different from J&J and the other mRNA vaccines in that it does not at any point cause your cells to produce the spike protein. Instead (as you said) the spikes are cultivated in the lab using moth cells and then injected into you.
Moths are considered unclean per the Biblical list of clean and unclean animals. That would be a problem for some people with respect to something like Novavax.