Subfactions are factions under factions rule or in faction teritory. They can still have rulers and have members.
Moredain after War of Ring didn`t loose any teritory, but they lost many of their best fighters and many chieftains in war. Soon fights between tribes and inside tribes began which weakened Moredain big time while their neighbours in south Tauredain who didn`t participate in any wars were united and stronger as never before. While in north Haradrim were united too and conquered Khand lately and now marched in south too conquer savannah once more. Tauredain soon joined and they split Moredain up. Haradrim were kinder because of previous aliance and they allowed them to retain most of their culture and beliefs while Tauredain weren`t so kind.
Limwaith were fishermen people who lived in mangrove. They fought with Sauron`s forces in War of Ring, but they warriors were few because they didn`t want to send more and they wanted to defend if Tauredain atack. The loss of War didn`t affect Limwaith much. But later they were conquered yet again by Tauredain who made massive genocide against Limwaith. Now really few in numbers and most of them slaves Limwaith seek revenge.
O`Khasis was powerful kindom in north eastern Rhun with powerful navy and good relations and trade with Orocarni that made them rich. But when Khamul III was invading kingdoms of Rhun into one big empire he atempted to do something nobody could do before annex O`Khasis. He did and took all fleet and wealth boosting his power. But the ruler of kingdom was able to escape with few thousand of his people. King Isildur II let them in his lands and made him governor of province of west Eregion.