Vietnam Trip better weather dates?

Planning a Vietnam trip with friends and trying to decide between:

🇻🇳 Late July / early August
OR
🇻🇳 Late August / early September
Route would be:
Ho Chi Minh City + Da Nang

Main priorities are:
nightlife
beach
adventure
Hai Van Pass
Hoi An
Riding mountains on Bikes

Which timeframe would you guys personally recommend weather-wise?