I'm not sure where you get the idea it's a much less powerful engine, it's not. The standard Porche for LMP1 had a 500bhp ICE output driving the rear axle and 400bhp from the mgu-k driving the front axle. It's a 900bhp car as standard, well actually they themselves described it as an over 900bhp combined engine and hybrid system combined, they removed the fuel flow limit and had 720bhp from the ice and 440bhp from the mgu-k including a 8MJ battery.
The Porche engine is significantly more powerful than an F1 engine, it's got a minimum of 10% more raw power but at no time had to save fuel.
If you uncorked the F1 engine just by changing fuel flow you'd also increase engine power, probably by a similar 40% or so and yes that would be more powerful.
They added two DRS systems to reduce drag and the all wheel drive almost certain ensures less wheel spin and more ability to lay down power on corner exit. It actually says that is just among the improvements they made because essentially this car follows no regulations at all, so they may have made it substantially lighter also.
EDIT:- was typing when the above video was posted, as said, it's being described as a 1200bhp beast, it's substantially more powerful than an F1 car and an F1 car following all regulations is only a tiny fraction slower.