im not going to pretend im smart enough to understand the backend difference between safari/chrome/firefox - firefox mobile hasnt been a great experience for me, but i dont use the browser on my phone all that much. at home, its vivalidi because it works well. im not knocking firefox, its been my go to browser for over a decade - but its been seemingly backed by google this whole time? i dont know.
If you're on iPhone there is no difference in the tech under the hood, because apple only allows webkit. Anything besides Safari is essentially Safari with a skin. The difference in tech is rarely the issue though. It's the monopolistic practices of Google and apple that should concern us