Yeah, I get it that lighter would be better. But you said 150kg if that's you, the bike, the battery, the motor and the cargo, then the typical 9c type dd motor will do you just fine, particularly in 20" rim.
I used the same motor as the trike kit in this bike, but a rear motor. 9c type motor from Ebikekit, in the 10 turn winding. Top speed was 18mph, so it could climb at 10 mph without making a lot of heat.
Bike, including up to 40 ah of battery was 100-120 pounds, me about 190. so nearly your 150k there with no cargo. Then the bike easily climbed my nearby test hill. 5 miles long, grade starting at 1% for a few miles, then 3% with the last two miles 6 to 8% grade, towing a 100 pound trailer. About 2000 feet of vertical gain, with no flat or downhill resting. just a long grind getting steeper and steeper. It kills geared motors easy peasy.
Never tested the limits beyond that, since the trailer was maxed out. so about 180 kilos, and the 9c type motors will do the climb in 20" wheel. This changes though, if you need to climb a mile or more of 10 or 12% grade, which is why I mentioned larger motors that can take 2000w or more for more than 30 min.
If you have trouble finding the slower wind 9c motor, it will still get to the top of a long 6-8% hill fine. It will just get a bit hotter, but not overheat. About 180kg is the limit for those motors in a 20" wheel. Just don't get the very high rpm version. 7 turn will work, just don't get into 5 or 6 turn.
If your hills are short, like half a mile, with a half mile down to cool a bit, you will be able to climb steeper hills. I speak only of limits to the motor on hills that are miles long, or more than 300 meters tall.
If your hills are not even close to 5% grade, and short, like a kilometer or less, then you could get away with a geared motor like in the bike you showed. That rig is perfect for amsterdam, but not san francisco.