Serious question - why are there different separatist parties for provincial and federal elections in Quebec (I know that the BQ were formed for the 1993 Federal election - at time when the independence movement were at its peak)?
Wouldn't it make more sense for the PQ to run candidates in both types of election, rather than having two parties with (potentially) different ideas?
Short answer: The Bloc happened by accident.
Long answer: The PQ formed before Canada had a formal constitution. They had a simple plan at first:
1) Win a provincial elections
2) Win a referendum
3) Negotiate secession
Federal politics were on the back burner.
In 1982, Canada enacted a formal constitution, but the Quebec government never actually approved it, which was problematic and caused legitimacy issues in Quebec. In 1987, PM Brian Mulroney negotiated the Meech Lake Accord with the premiers. Meech Lake was a series of constitutional amendments designed to get the Quebec government to sign off on the constitution and increase federalist support in Quebec.
Meech Lake fell apart (rather spectacularly), and more or less killed the Mulroney government. Several nationalist MP's (both Tory and Liberal) quit their respective parties to sit as independents in response to how they thought Quebec had been mistreated in the negotiations. These independents later caucused together as the Bloc Quebecois.
Eventually they formed a separate party to advocate for Quebecois interests and separatism at the federal level. They won a by-election in 1990, and 50+ seats in 1993, but the whole thing was never at the Parti Quebecois' initiative which is why they are two separate, but closely allied parties.