My Cube Agree Hybrid runs the Fazua system. In standard form with, bottle cages, Cycliq lights front and back, Garmin Radar and head unit (1030), in size 56cm it weighed 15kg (checked when flying back from Spain). I have a recollection of it having a saddle bag on there as well, but I can't be sure.
Mine assists up to 25khm/15mph at which point there is a soft-ish cut off. It's not instant gone, at least to me, it's more of a roll off, all be it quite quickly over 2 to 3 seconds. The reverse happens when you fall below the limit. Although heavy by today's standards with regards to road bikes it does not feel dull without the assist running on 32mm tyres.
I currently weigh in at a small, for me, about 125kg (slowly getting smaller). Over the weight limit for the bike and wheels no doubt

. But this is to show you how the bike runs for me.
I did a 75km ride with just shy of 1000m of climbing and arrived home with 40% battery. I try to only use the motor on hills I can't ride up. On the flat and upto about 6% I rarely use the assistance. I can carry a speed of >25kmh/15mph for a fair way on the flatter roads but once it starts to go up, even only 2%, that speed drops off. I can't recall exactly how much I used the motor but I only really had maybe 5-10km of road with sections higher than 6% and I only used the lowest power level I could get away with assist.
I want to get fitter and lose weight, it seems to be working

, I set a PR on a 2km hill at the start of my ride without assist (the previous best was with assist

). So generally the way I use the motor is no assist for as long as I can get away with, then the lowest level I can get away with,

. It doesn't make me much quicker, but it does mean I can ride for longer.
Whatever system you go for find the way it works best for you and make the most use of it, Oh and enjoy the zip along feeling