I wish to know if the transaction fee is taken from the amount I'm sending or from the amount remaining in the wallet.
For example, let's say I have 1.5 btc in the wallet.
If I input to send 1 btc, will 1 btc or 0.9999 btc be delivered?
It's taken from the remaining funds in your wallet. So when you enter 1 BTC, then 1 BTC will reach the recipient and your balance will be reduced by 1 BTC + transaction fees.
And what if I input 1.5 btc (i.e. the total amount of the wallet)?
Thanks
The send screen will then inform you, that you do not have enough funds to complete the transaction (since the transactions fee cannot be paid). It will offer to send "everything" instead, which will set the amount to "all funds in the wallet - required transaction fee".