Honestly I expect the overall laptime to be about the same as current after a couple seasons. I'm just guessing too though.

They'll probably gain some speed in low/medium speed corners, and lose speed in high speed sections. Although additional active-aero will help some.

They still have access to 1000 BHP for short periods, while weighing less and having less downforce that will almost certainly result in less drag for most cars. I would not expect peak speed to be that much slower than now, just average speed over the lap.

Sure the drop to 6 gears from 8 (if it goes ahead) is going to hurt but not being able to use all 1000 BHP on the straight at somewhere like Monza means you'll just be a sitting duck all day long, RB have shown that when they had their biggest DRS advantage.