Just consider that the Napoleon Pass is OFFICIALLY closed to hikers until at least 1 April each year. Snow is regular and deep. It is hazardous.
After 1 April, local authorities assess the weather and conditions at the Napoleon Pass daily. So, it can be hit and miss. Check the weather and remain flexible. The Pilgrim Office in Saint Jean Pied de Port has the latest forecast and conditions at the pass.
For reference, in 2020, Easter is on Sunday 5 April. As a general statement, each year on the
Camino Frances there is a "pig in the python" scenario, where a large number of pilgrims start a Camino as they have extra time off from work. In most of western Europe, people have off on Holy Thursday, Good Friday, Holy Saturday and Easter Sunday and Easter Monday (day after). So that is five days off work starting off. Many folks toss in a few 'bridge' or personal days to make up to a two-week period for doing Camino.
My advice to avoid this added surge and the burden it places on all Camino resources, is to avoid walking during the Christian Holy Week, immediately before Easter, and the immediate week following. In 2020, that means starting your Camino on or after 12 April.
As regards walking through the Napoleon Pass, that should mean that the pass is officially open, but subject to local advisories and control.
Hope this helps.