First you will be asked KYC including DOB, address, photo verification to be able to use any function.
1: Deposit/Withdrawal (earn interest rate)
BTC 6% interest rate per annual upto 5BTC, 3.2% for 5 <
For more detail
2: Loan function
Collateral = BTC
LTV (Loan To Value) 50% = 12.5% per year
LTV 35% = 10.44%
LTV 20% = 6.73%
3: Trade function
I always have a doubt using 3rd party app for deposit since the case of exchange/ 3rd party app hack.
Good thing about BlockFi is relatively high interest rate. 6% BTC, 4.5% ETH which is higher than MakerOasis DAI saving rate (0% now but 6 - 8 in regular case).
Maximum collateral amount is 50% e.g. 1000USD collateral to borrow 500USD but with high interest rate. it can go as low as 20% collateral.