The first of those subtle alterations has to do with the thresholds to qualify for delegates. Statewide, a candidate must reach 15 percent of the vote to receive any of the at-large and automatic delegates. A new wrinkle for 2016 is that the party has inserted a lower threshold of 10% as a fall-back option should no candidate surpass 15 percent of the vote. This is not an uncommon response on the state party level given how large the field of Republican candidates was when rules were being finalized in the late summer/early fall of 2015. But as a field winnows, the necessity of that fall-back, lower threshold decreases.
There is no winner-take-all trigger in Mississippi for a candidate who wins a majority of the statewide vote in the primary. However, there also is no prohibition on a backdoor winner-take-all scenario. If only one candidate receives more than 15% of the vote, then that candidate would claim all 28 at-large and automatic delegates. The usual winnowing caveats apply. As the field shrinks, so too do the odds that only one candidate will receive more than 15% of the vote.
At the congressional district level, there just one threshold; a winner-take-all trigger. Should a candidate receive more than 50% of the vote in any of Mississippi's four congressional district, then that candidate is entitled to all three of the delegates from that district.