Is it okay to arrive in Europe with less than 400EUR?

The bad news is that some Brazilians went through the taxing, unpleasing experience of being sent back home directly from the airport, although they did not have a need for a visa. There's a small but well established community of illegal immigrants in countries like the UK or Spain. So, both countries will scrutinize you closer.

Take an international credit card with you, if possible. Otherwise, the 400 euros would be definitely too little. That's 18 euros/day.

If you are young, make sure you have a way of explaining why you would want to come back. Are you working, studying?

If you are visiting someone who is illegally in the EU, don't even mention this visit.

Don't bring anything that a tourist won't really need. They can go through your luggage and inspect any single item. So, do not carry family photos, CVs, clothes for a year, any Brazilian food, addresses of companies, and so on. All these things could raise a red flag.

Answer all questions at the border in a concise but precise manner. They don't want you to tell a little story, just basic facts. Sometimes border control agents start doing some small talk. Do not assume that they are just being friendly, they want to get information from you in an informal way.

Do not lie about anything. Often they already know the answer to the questions, and are just testing you.

I know many people who have traveled to the Schengen area without a lot of cash and none of them have ever been required to demonstrate a proof of funds. Millions of people travel with just their credit card these days, so they won't be able to show any cash anyway.

What I would do is say you have 400 Euros in cash and have the rest in your bank account. No need to explain your story about Transferwise as that would just complicate things. I presume you do have money in your bank back at home, so this won't be a lie.