Repulsorlift technology has no height limit except the one imposed by the gravity well
STAPs are lightweight reconnaissance and patrol vehicles used by the battle droids of the Trade Federation army (and later, the Separatist Alliance). Incorporating repulsorlift technology, the STAP (single trooper aerial platform) is a slim, agile craft sporting a pair of blaster cannons. STAPs are often deployed as support vehicles in conjunction with larger craft.
That was your example of a craft levitated to great heights with repulsorlift but there are other, much heavier vehicles, with that technology:
So it seems there is no limit to the achievable height with an amount of repulsor engines large enough... except possibly one: the size of the gravity well. Repulsor technology seems to work pushing against a gravity so it doesn't work that well as gravity comes close to 0. Yet Core Ships can escape orbit in planets the likes of Geonosys and we don't know any example of a height limit in a smaller planet.
As pointed in the comments the list of ships with repulsor technology is larger and respulsors can be powerful enough to even be weaponized with large destruction as a result.