I'm playing on Expert mode so I don't see requirements for conversation checks and so on.  Can someone tell me a few details about how they work?  Does it use the character with the highest stat for the check or always your PC?  Like if there is a conversation check for Int 16 and your PC has 12 but one of your party members has 18 can you select that conversation option? 

 

Does it matter which character is selected when you initiate the conversation?

Always your PC in convos. Doesn't matter who is selected to start the interaction.

 

In scripted interactions you may be able to choose an NPC for performing a certain task  that has requirements.

So if I want to pass conversational INT checks, for example, I must have a high INT main?  Ok, thanks.

So if I want to pass conversational INT checks, for example, I must have a high INT main?  Ok, thanks.

Yep. It always checks your main.

One addendum to this is that sometimes scripted interactions check everyone in your party. If you've got to jump over a broken bridge to progress, you're not just sending the person with the highest athletics, yeah?

Though remember its not just attributes, conversation checks also look at race, class, gender, culture, and more

 

see here:

 

Pillars of Eternity: Special Dialog Options