Most likely. Briliza connects through GoCardless, a regulated PSD2 provider covering banks across the European Economic Area. You see the full list for Spain when you add an account.
No. The connection is read-only. Briliza can see your transactions and balances, and can never make a payment or move a cent.
Yes. Accounts from different countries and currencies sit side by side in one overview, converted to the currency you choose.