maybe I've not been clear enough
I mean: if i buy a checked baggage option, is there any difference if i buy it directly during the reservation of my tkt or after have booked the tkt (both online)?

in the first case, I'm buying it when I buy the tkt, adding the service at the same time.

in the second case, it should be through "manage my bookings", then adding the service and making a separate transaction.

Edit: got it;

"***Higher prices apply if purchased through Manage Booking".
Ryanair suc*s!