It's a few years old now, but my answer on the point still effectively stands. Basically, Trekker groups--whether part of a larger body of voortrekkers, or natrekkers (those who came up a bit later)--sought independence not only from British governance, but also from each other's potential dominance once the immediate perils had dissipated. In Natalia 1842/3, the British followed them; most went up-country. In the Orange River Sovereignty the period up to 1854 involved actual fighting before a compact was reached recognizing self-governance, and the Orange Free State that resulted was for a very long time the richer and stabler republic. It's the South African Republic (Transvaal) that was the really fractious one, with groups of freebooters and landhunters creating new 'republics' all over the place in the 1880s, and occasionally fracturing the state in the early years up through the 'burgher wars' of the early 1860s. My answer up there deals with unification efforts, and why they didn't work, but also gets at how little some groups of Boers really wanted to do with other groups for a variety of reasons. In the SAR/Transvaal itself, for example, the town of Schoemansdal in the north (originally Zoutpansbergdorp)--founded by Hendrik Potgieter, who was exactly the kind of military dictator in being that made many trekkers wary, and made him a hard person for civilian authorities to work with--was despised for slave-trading and general moral turpitude for a long time. When Venda hostility and action forced its evacuation in winter 1867, the reprisal raid under Paul Kruger (then Commandant-Generaal of the Republic) got barely any volunteers when the commandos were called up. Only gold, first in small quantities around Lydenburg and then the big strike on the Witwatersrand in 1886, gave the government in Pretoria the ability to press its will. Even then, some Boers sought to escape it, and trekked even further north, or went into German territory, or something else.

Although there's a deep irony that most of these same groups' leaderships had little trouble lording themselves over non-whites in lands they took (when they had the power to do so, which was not as often as you'd think), many of the rank and file were deeply devoted to the idea of a devolved consultative state, and it didn't take long for that to coalesce into many centers--but of course if one developed major resources, like the Transvaal in the 1880s, it would happily try to absorb places like Stellaland, Goosen, de Nieuwe Republiek, the two Klein Vrijstaten (and possibly a third carved out of eSwatini in the 1890s), et cetera.