https://www.cryptonator.com and
https://www.coinvault.io really look professional but it is not advisable for you to leave your coins with an exchange for too long of a time.
Is there anybody with information whether these online wallets can stake coins that are stored with them?
Hi CoinVault team here,
You are right the general rule is if you don't own the private keys you don't really own your funds.
CoinVault does not hold accessible copies of private keys, only encrypted copies which are useless without the wallet password.
The wallet HD seed is encrypted with the users wallet password (which goes through 64k rounds of a KDF function and a strong salt) we then store the encrypted data only.
The user has to provide the wallet password to be able to sign transactions.
This still requires trust in the developers code (which applies for many wallets out there including hardware and offline wallets) but the attack surface is reduced dramatically.
I am happy for any feedback you have on the wallet
coinvault.io team