P&L on CFD positions is computed according to the Open Trade Equity (OTE) convention. OTE refers to an accounting convention commonly applied to derivative contracts such as CFDs and futures. In accordance with this convention, the unrealized profit or loss calculated from the point at which the contract is opened to that at which it is closed is aggregated as a separate line item in the account equity balance. When the contract is closed, it's OTE is applied to the cash balance, with a gain increasing the cash balance and a loss decreasing the cash balance. This convention is in contrast to the Variation Margin method under which the profit or loss is continuously applied to the cash balance.
Regardless of the convention used, account equity and position profit or loss remain the same.
Trading commissions are not deducted from the P&L computation on CFD positions. Instead, trading commissions are deducted from the cash balance on the account and will appear as a separate item in your statements under the Cash Report section.
Disclaimer: CFDs are complex instruments and come with a high risk of losing money rapidly due to leverage. 57.9% of retail investor accounts lose money when trading CFDs with IBKR. You should consider whether you understand how CFDs work and whether you can afford to take the high risk of losing your money.