Does hand gesture have an impact on meditation or attainment of Nirvana?
Yes and no.

Certain hand gestures cause better energy flow through your body and vibrations. These vibration can be some times an aid in dissolving pain and also fabrication.

If you get attached to the vibrations and gestures this will do more harm than good in your progress.

So my advice is do not bother too much about these as their contribution to your final goal is marginal or non existent through it might give a mild boost to better practice in certain situation is making you conferable to be seated for a long time by creating Piti which is one of the enlightenment factors but keeping in mind you cannot bake a cake with one ingredient and attachment to the feeling or creating view and perception around the gestures will hold you back