Nagato's only chance is to defeat Madara before PS comes out, which is highly unlikely considering Madara read the tablet and has prior knowledge of the Rinnegan, so he doesn't need intel on Nagato himself to know that he's up against a big threat and Madara's moveset is very limited with only EMS. Once PS comes out, he tanks all of Nagato's attacks, cuts Chibaku Tensei with a PS sword slash and then ends Nagato with 2 swings of his blade.
The same applies to Scenario 2, but if he decides to summon Kurama against him, its clear Nagato stands no chance at all. His animal summons are fodder to PS or Kurama alone let alone them together, they all get taken out by PS's sword slash and Bijuu Dama's explosion turns the Cerberus summon to ash, it surviving this is a laughable outcome. Nagato dies the same way he does above.
Gedo Mazo doesn't help him in any of the scenarios as PS outclasses it.
Madara mid diff without Kurama, low diff with it.