1. When you purchase a ticket on united.com you will received all applicable EQM/RDM according to fare and class.
2. When you use Choices to received credit on your credit card for a ticket purchased on united.com, it is done by Chase and not by UA. Therefore, UA will have no idea of your Choices transaction other than you used miles/choices and your balance has gone down.
3. Be prudent, because some purchases are not redeemable by Choices such as the RCC membership (even if purchased on-line).