For all supported coins, the BitBoxApp offers you 4 different "Priority" options (fee levels) on the page where you create your transaction:
These options are based on our own node's fee estimation (for bitcoin) or on the estimations of https://ethgasstation.info/ (for Ethereum). If you want to choose a custom fee rate, go to the BitBoxApp settings and enable "Enable custom fees". Do note that if you choose a low fee, it might take a long time until your transaction gets confirmed on the blockchain.
Please check a block explorer like https://mempool.space/ or https://etherscan.io/ for current fee rates.