> What makes an mRNA vaccine more appealing than a protein-based one?
Having worked on the same targeting mechanisms for protein based vaccines meant to be personalized cancer therapies, and having followed the mRNA vaccines with envy, the benefits are absolutely massive. But there's not a single alternative. In comparison to each type:
Short peptides injection are worse because: minimal immune stimulation, less of a mechanism to train the immune system on the peptide targets, have not been effective.
Viral delivery of mRNA, that makes proteins, or more exotic methods like yeast with modified genomes: this is a traditional vaccine with a custom viral genome with the peptides of interest added as part of the viral genome. This is not directly a protein virus, but it does make the cells it infects produce the peptides. This requires cell culture to grow the virus, which requires a unique clean room per vaccine, which can be impractical and expensive for a custom virus. It's also very very slow to produce, QC, and make sure it's safe. mRNA production is faster, cleaner, safer, just all around better in every possible way.
As for your other questions, sure they are interesting, but get ready to gear up and read tooooons of literature. Most people don't have any of these questions unless they have a deep distrust of the technology, and don't trust that others have bothered to investigate.
Skepticism is good, and if you are truly curious I really applaud you and encourage you to pick up an immunology text book so that you can also read and understand the papers. But mRNA vaccine skepticism has to be the stupidest "skepticism" and falsehoods I have ever seen of a new technology. As the competitor to what I was working on, I must concede that it's better on all metrics, and I am kind of saddened for humanity that all these lies about mRNA seem to dominate over the true and huge technological advancement that has occurred.