Seems like you are referring to sex. Obviously, when you are living in multi-generational households, you can't be having loud sex on the kitchen table. You can either do it quietly in your bedroom, or use the Asian practice of going to love motels when you want to let the monkeys loose.
Regarding your second point, I'd like to point out your particular phrasing which makes clear your point of view, that you consider a multi-generational house "someone else's house". It would be your home that you are living in, even if it is not your name on the deed or rental agreement. Now, whether you can develop your own relationships and life and way of doing things has to be independent of whether you are living with family. For every person that is an example that living with family is a burden, there surely is another example where it is a benefit. The growth in your relationship with your family can be hindered or accelerated by your time with them, I don't think there is a one-size-fits-all answer to that.
Regarding your second point, I'd like to point out your particular phrasing which makes clear your point of view, that you consider a multi-generational house "someone else's house". It would be your home that you are living in, even if it is not your name on the deed or rental agreement. Now, whether you can develop your own relationships and life and way of doing things has to be independent of whether you are living with family. For every person that is an example that living with family is a burden, there surely is another example where it is a benefit. The growth in your relationship with your family can be hindered or accelerated by your time with them, I don't think there is a one-size-fits-all answer to that.