Please could somebody explain how the PASO works? Like will the highest scoring internal list become that alliance's formal list in the general election or would the final list be a mixture of internal lists?
Yes
It's up to each individual Coalition in each individual province, and you also have to take into account the mandatory gender parity law, which means that it's a complete mess
Using Corrientes as an example:
ECO+Vamos Corrientes (JxC)
for Diputados: D'Hondt system with no minimum threshold
for Senators: full-list system, ie winner takes all
FDT D'Hondt for all posts, with a 5% threshold
Vamos D'Hondt for all posts with no threshold
Is the process how the final list will determined on the ballot (ie what is the threshold) or the voters have to find out by themselves?