you can create different universe for different sources and 
link them in BO.

Yes. When you pull data from different data souces, if the 
dimension name is same then they get linked automatically.
Ex. You have "Month" in one DP1 and Month in another DP2 
they get linked automatically. i.e. a Join is created 
between the two. If the name is not same then we need to 
link them in Data Manager.

we can work with different datasource through Business view.

if we are creating two universes and linking them , they 
should have created on one data source.