There are uncertainties in almost all visa category except K1 and H4. Under K1, the procssing time is around 10 months and for H4 the procssing time is 3 months. However, if someone is trying to come on someone's greencard (immigrant petition for spouse), the prcessing time is >22 months.

So, best is to get married on H1 or wait till you have citizenship approved. Following site has stats showing 99% approval for H4 for Nepalis in 2023. Interesting stats worth sharing.

https://visagrader.com/visa-approvals-and-refusals/H4/nepal-npl