It depends a lot on what you want to highlight in my opinion.
One way to โunrollโ a pie chart over the time dimension is to use a stacked bar chart (which is the default in plotly express). This approach would highlight the proportions over time. Here is a link to the documentation.
Yes, and you donโt need to specify x if it is the index eitherโฆ
If youโll have 20 assets, then just make sure to inform the users to click/double-click on the legend to isolate the plots. It makes it easier to compare 2 assets over time.