Yes, you get the vouchers even for low cost direct AA tickets, it's related to your silver card, not the ticket arrangements. You may need to ask though (in all circumstances) since it's not always intuitive to the staff.

For irrops AA are excellent in terms of getting you rebooked to your destination efficiently. Mainly from plenty of practice. If it is weather related there will be a good chance it's a downgrade to Y, with a distinct element of "you're not seriously complaining about the downgrade are you?". You would certainly get the TPs of the flown journey, you can try to get the TPs of the booked journey, reports vary as to whether that is successful or not.

The fact it is a TA booking is fairly immaterial to all of the above, by the time you travel it's a ticket like any other.