simply, 88 bytes

It's a long mess, but works!
(I've used \n for style, but an actual newline works as well, and that is reflected in the size of the answer.)

fn($L){$T=" X\n"&array_map($L,fn($V)each$x in run&format("%'08s2"&cb($V,16,2))out$T[$x])}

Creates an anonymous function that outputs the result.

This works by left-padding all binary values to 8 characters, then ends with "2".
For each character of the binary string, it outputs the n character in the string " X\n".
For 0 outputs " ", for 1 outputs "X" and for 2 outputs "\n".

Example

$fn=fn($L){$T=" X\n"&array_map($L,fn($V)each$x in run&format("%'08s2"&cb($V,16,2))out$T[$x])};

run $F(["FF", "81", "47", "99"]);

Should output the expected result.

Slightly more readable

Both versions do exactly the same.

fn($list) => {
    &array_map(
        $list, fn($line) => {
            $translation = " X\n";
            $temp = call &format("%'08s2", &convert_base($line, 16, 2));
            each $char in $temp {
                echo $translation[$char];
            }
        }
    );
}

For some reason, JavaScript doesn't like the original order, when I untangle the code.