Uli,

Do you have previous mountaineering experience? Mont Blanc is an “intermediate” mountain, but you absolutely need experience. I recommend checking out this article: https://www.theatlantic.com/international/archive/2012/07/why-is-mont-blanc-one-of-the-worlds-deadliest-mountains/260143/

Hi Uli, there are rules and regulations on place from french authorities in regards to minimum equipment and even hut reservations (not sure if this will be enforced in 2021). You have to make sure to check these.
Access to the mountain is regulated and there is police on the scene at Tete Rousse.

Starting from Bionnassay village might be an alternative you want to look at. The way up is nicer than going through the Les Houches ski resort.

Best time is during summer months, but there is no way to balance good weather and low numbers of other climbers. It is an either or decision.

Although Montblanc has got the name and altitude to make it a tempting goal, there are plenty alternatives in the Alps with similar vertical ascent and more freedom to it.