I think you're going to need to provide more information before you get many answers...
For a start, an update from which version? If 26.0 or 26.1 then the changes were largely 'under the hood' and not likely to create these kinds of problems. If from an older version, it would be useful to know which one, so that we might have an idea of what's changed. Even then, the core applications haven't changed much, other then general UI styling (e.g. Liquid Glass), but that doesn't sound like your issue.
As for the specifics...
> Can't figure out how to access different email addresses
In which email application? Mail.app? Outlook? web-based mail?
> Unable to display Favorites as previously via Safari
What did you previously do to 'display Favorites' that you can't do now?
Safari still supports the same bookmarks, favorites bar, etc., and it's not clear what you're seeing (or not seeing) that's different from before.
Also worth mentioning is what device you're using. Your original subject line says 'iOS 26.2', but you reference Tahoe, which is specifically MacOS...