What's better? Many small TS cols or one large TS col?


I am scraping a lot of time series data from the web. I have multiple “mother” time series with say 10-20 sub-timeseries; for each mother ts, I created a separate ts collection. Now, I am asking myself, would it have been better to simply create a single large ts collection and dump all timeseries into that one, simply differentiating them with an extra column or metadata label or sth like that? In practice, I typically want to query data for all ts. I thought it might be faster, if I do separate smaller queries, connecting to each individual collection, instead of doing one large query? Now, I am not even so sure anymore, whether this would bring an advantage in timing? in ts cols, how does the query time scale with the size of the col? Also, I figured that I might want to query my data with dask-mongo, i.e. use to dask to query the data piece by piece. This would be much easier with a single col, so I am thinking of now migrating the content from all the small cols to a single large joint col. What are your thoughts on this? =) thanks!