how to create a file and make it executable in one command?

Here's one I have saved in my shell aliases.

nscript() {
    local name="${1:-nscript-$(printf '%s' $(echo "$RANDOM" | md5sum) | cut -c 1-10)}"
    echo -e "#!/usr/bin/env bash\n#set -Eeuxo pipefail\nset -e" > ./"$name".sh && chmod +x ./"$name".sh && hx ./"$name".sh
}
alias nsh='nscript'

Admittedly much more complicated than necessary, but it's pretty full featured. first line constructs a filename for the new script from a generated 10 character random hash and prepends "nscript" and a user provided name.

The second line writes out the shebang and a few oft used bash flags, makes the file executable and opens in in my editor (Helix in my case).

The third line is just a shortened alias for the function.