You cannot add multiple rows in one Sheets action, unless you write a script in Sheets.
The solution is to use a For Each loop to repeatedly call “Add row”.
After the condition you mentioned, use a “For Each” loop action. Inside that action you can call “Add row to Sheets”.
Do not use your second attempt at the code…multiple loops over the same thing is almost never right.
Your code might look something like this:
{{getCustomerDataForeachitem.firstName}},
{{getCustomerDataForeachitem.lastName}},
{% for tags_item in getCustomerDataForeachitem.tags %}
{{tags_item}}-
{% endfor %}