major hotels in Japan need to commit to tour agencies blocking out their rooms for Sakura season, which is what hanami 花見 loosely refers to.
I think I got used to staying in quieter places. Shibuya is not a bad place, near big train station and all just a little too "hot"
I always put off planning a hanami holiday due to the logistic problems it presents. I do koyo season already. I plan to try another one soon
tbh Ueno side is even better. Less chance of running into drunk folk also
I can't remember exactly but one of Shibuya and Shinjuku have more eateries run by Chinese nationals.
6 days depend on your budget for meals and shopping. If you want to have an accurate estimate, do some planning and see what spotlight meals you want to try. Shopping, use card where accepted.