Bus or plane from Ulaanbataar to Beijing

Hey dear community

im going on an Adventure this october. Ill be going to mongolia for a 2 week horsebackride through the altai mountains.

After that when im done im thinking of taking a plane to Beijing for a 2-3 days and then id love to take a Train to Shanghai.

To my questions - i have seen there is also a train + bus route to Beijing. Im a bit hesitant to take mongolian bus ride because - to state the obvious - im not Feeling quite safe and comfortable to sit in a mongolian bus for 9 Hours, on the ether Hand im sure this will be a once in a Lifetime experience. Would you say its worth it, has anybody ever done something like that here?

Does anybody know if this is a scenic road from Zamyn-Üüd to beijing (havent seen anything on google) because its not About the money for me. Its about experience but also making the most of my time there.

Also is it worth to stay for 3 days in bejing? (approx. 1st of nevember until the 3rd) whats a cool district te stay in - i have seen sanlitun this seems like a fun place? to Keep in mind im 23m - (24m when im there) and love photogcaphy, great Food and "Young" Areas - so this should fit the criteria right?

after the time in Peking i either want to take the Train to Shanghai or Hongkong - out of experience what did you like more? im hoping to make the most of the time and i think if i take so many trains ill miss out on about half a day (Peking - Shanghai 4 Hours dicect Train and te Hongkong about 8) or is this irrational?

is there a place i am missing, something more worth it, something i have to see that i havent thought About??

After that ill fly back home to Vienna