> 2. For standalone scripts... well, I think it's best to reach for a proper programming language (e.g. Python) instead of any shell language, but if I had to use one, I would pick bash. Sure, it has many footguns, but I know them pretty well. And fish language is also not ideal - e.g. IIRC it doesn't have an equivalent of `set -e`, you have to add `; or return 1` to each line.
I'm sure you know this, but: no particular reason the interactive shell you use has to match the shell you use for scripts. All of my scripts are in bash, but I haven't used bash interactively in decades now, at least on purpose.
I'm sure you know this, but: no particular reason the interactive shell you use has to match the shell you use for scripts. All of my scripts are in bash, but I haven't used bash interactively in decades now, at least on purpose.