When I search for Fixed Deposits on totalmoney.pl , Nest Bank (previously Smart Bank) is always coming up top in the list because they are offering good interest rates.
Is this bank good? Is it covered under any kind of Insurance from Polish National Bank (NBP) ?
You will have to make your own judgment about whether it's good or not - it's the newest, smallest and least capitalised Polish bank but it has a rating similar to most of the rest.
Yes it is covered by the NBP insurance scheme - I would not read too much into that because if things go really wrong it's unlikely the Polish state has the money to cover losses. There have been some small banks (more like credit unions) going bust in the last two years and it has not been easy for depositors to recover cash, I think they will get it but I have heard anecdotally that the ones who have emigrated are at the back of the queue.
I use Nest also as I like the no-fees for cash withdrawals at all ATM policy, and the account+card are free, no strings attached (no min monthly pay-ins, etc) - no problems thus far...
They are the worst bank ever, I had an account with them, and one day they closed it for no apparent reason, one person said I violated the account terms, when asked what I violated they couldn't say, another person said I'm a high risk customer but couldn't explain why, they are a horror.