I like the idea with the videos. and you present them well. I want you to read this post/request as feedback for your next vid to be better. Thank you making it and posting it.
The technical geek in me would love if when you do the next test, you ID the Prop specifically - what brand, what pitch etc and as before the diameter. the Area of a 10" prop = 314 si, vs 9" = 254 si, a ~125% increase in area from 9" to 10". If there is a way for you to measure Amp draw, that would be interesting to note. Please include the weight of the batteries. I find it suspect that the 3s 1500 mAh battery in first video is the same weight as a 4S 1500 mAh battery. Last suggestion - possibly a labeled shot of you setup too. so others can do their own experiment.
I enjoyed your overdub, and the footage was great. Keep it up.