If two things say "You may pay (cost)" and I pay that cost once, do both things happen?
If you don't pay a mana the second time you are instructed "you may pay {R}", you do not get a second token.



When the creature enters the battlefield, the abilities of both Flameshadow Conjuring trigger. You place them on the stack in the order of your choice.

Only one spell or ability resolves at a time.

First, the newest instance of Flameshadow Conjuring's ability on the stack resolves. As part of resolving, it gives you the option to pay a cost, and creates a token if you do. 

Later, the other instance of Flameshadow Conjuring's ability resolves. As part of resolving, it gives you the option to pay a cost, and creates a token if you do.

Neither of these abilities care about costs payed by similar abilities in the past. They just check if you payed the cost they gave you the option of paying.