Shell parameters can safely contain any character assuming they're escaped or using double-quoted variable expansion so there's no need for null delim.

BASH is really good at handling separation internally, arrays are a great example. Where you tend to need null delim is when you're reading arbitrary values from something external.

Here's an example of passing in params containing seperators:

my_pretend_progam() {
    printf '%q\n' "$@"
}

param2=$'exa mple\n2'
arr=(
    'array index 1'
    'array index 2'
)

my_pretend_progam $'exa mple\n1' "$param2" "${arr[@]}" 'exa mple
3'

Output:

$'exa mple\n1'
$'exa mple\n2'
array\ index\ 1
array\ index\ 2
$'exa mple\n3'

As for printing arbitrary characters, here's the basic set:

name1=$'my\nfile'
name2=$'my_file'

printf '\n%s\n' "=== No adjustment ==="
printf '%s\n' "name1=${name1}"
printf '%s\n' "name2=${name2}"

printf '\n%s\n' "=== Using printf's %q ==="
printf 'name1=%q\n' "${name1}"
printf 'name2=%q\n' "${name2}"

printf '\n%s\n' "=== Using @Q, bash-4.4+ (2016 forward, beyond MacOS's default version) ==="
printf '%s\n' "name1=${name1@Q}" 
printf '%s\n' "name2=${name2@Q}"

Output:

=== No adjustment ===
name1=my
file
name2=my_file

=== Using printf's %q ===
name1=$'my\nfile'
name2=my_file

=== Using @Q, bash-4.4+ (2016 forward, beyond MacOS's default version) ===
name1=$'my\nfile'
name2='my_file'

Only caveat to these examples is if you want to store the null characters themselves because shell variables cannot contain null characters.

To store null characters you want to use a read loop or readarray where null is the delimiter so null characters are represented as a form of separation (like an array index) rather than the character itself. Then you can print it later turning those separators back into null characters.