Paldea map for reference
Ok, so a bigger breakdown.
1. The Path of Victory Road (gym challenge)
The grass gym leader Brassius is in Artazon, the town with the flowers and windmills. I'm guessing today's trailer focused on the right side of the Paldean map.
After looking through the trailer again I dont think Nemona has any relation to Geeta and may just be a passionate an of hers.
2. The Path of Legends (Arven's quest)
The rocky hills between Artazon (grass gym) and Mezagoza (school city) is probably where the Stony Titan Klawf is found. Klawf is like one of the lord fights from Legends. It will probably be tough to fight against them.
Gathering the rare ingredients is interesting. It may unlock Koraidon/Miraidon abilities that allows you to traverse the region further.
3. Evil Team Path
Mela is the commander of Team Star's Fire crew. On the map its between Artazon and the modern city with skyscrapers and has red flags. I'm theorising that there are 4 more commanders. The 4 other flags are pink, yellow, purple, and black. I think the pink is Fairy, purple is Poison, and black is Dark. Those seem good, mischievous deliquent types. The yellow one I'm unsure of but I suspect its Fighting, think of rough bullies that like to fight, etc.
4. Let's Go feature
Lets Go allows your Pokemon to follow you and act independently with its environ. It can collect items and battle other wild mons with your command (auto-battle). Auto battle feature is one of ways to take down Team Star grunts before you challenge oen of the crews commanders like Mela.