Two downtown
Downtown cap of two: Hoa Lo + history, or fine arts + Literature courtyards. Tickets follow the site; check closed days. Do not chain four museums. Use midday heat for indoors; dusk still keeps one outdoor close or a hotel return.
West city
Ethnology sits in Cau Giay / west city — bus or Grab half-day; budget walking in the outdoor house zone. Do not “make up for it” with Old Quarter night lanes after; close with one south or hotel-area meal on the way back.