The verdict
If people outside your team fill in the form and it needs to look like your brand, pick Fillout. If you have technical people, high volume or data rules that push you towards self-hosting, pick n8n for the automation behind it.
A sensible pairing is Fillout for the form and n8n for what happens next, using the webhook. If nobody on your team is comfortable with JSON and servers, use a simpler connector instead. I would not pick n8n just to collect a form.