This is an important question.
Salah is prescribed in the Quran. The Sunnah tells us Muhammad's preferred method of doing it. It is possible that the Sunnah method of doing salah is one of the best forms of prayer, and we can follow it if we want to.
However, we don't HAVE to follow it.
The ways in which Muhammad conducted himself (in salah, charity, etc.) are definitely good ways to do things, but they're most likely based on the society in which he lived. Thus, we don't have to follow them. However, if Muhammad's methods are practical in this society and they work well for us, then we can follow them if we like.