If you book with RCI you will not get the discount a TA would offer usually 10%. I have no problem getting my TA to obtain the price drops for me.
RCI and XCelebrity are now offering the first change free but any subsequent changes including at a charge of £35 or sometimes higher than this depending.
I think now that RCI and X have made the booking conditions clearer in that price drops should not be a problem in the UK any longer. I see now that they are also offering special rates for the Military or Armed Forces guests. They often offer these in the US. They are not available all the time but they do appear as specials etc.
Sue