Solo Travel

if a ~6h travel time is alright with you, i highly recommend Ha Giang City. it felt very rural for a provincial center. when i visited there years ago, the streets were very clean, cars, motorcycles, and people were sparse.
another great thing about Ha Giang City is that it is the gateway to more remote villages if you find the city too busy. just driving through Ha Giang Province was a delight, it was my first time passing through such expansive limestone structures.
the same can be said for many places nearer Hanoi. for example Ninh Binh, outside the more touristy area, has quiet towns dotted with limestone hills which make it seem like the land equivalent of Ha Long Bay.
in Hanoi itself, the most peaceful spot i visited was the Museum of Fine Arts. i really enjoyed taking in the paintings and sculptures there (and the quiet).
it can be a little challenging to talk with locals outside Hanoi because a lot of them do not speak English but i found most of them very helpful.
wishing you a great time there.