The Siemens QP series is a typical, regular modern breaker (1-pole per 1" space). It is physically identical to the Murray MP series, and some Murray and Seimens panels will list both on the label. The QP and MP will physically fit into and function in many panels, including the formerly-Bryant-now-Eaton BR type, Square-D homeline, and other out of production products, but strictly speaking they are only legal if the label says so.
The GE THQP series is a line of skinny breakers (2 poles per 1" space) which will physically fit only in GE panels for which they are listed. GE panels use this series to fit more circuits into a panel, instead of the tandem and quad breakers typical of other manufacturers. This is in contrast to the more standard GE THQL series, which resembles the QP, MP, BR and Homeline breakers and will generally physically fit where any of those do, albeit again not legally.
Eaton Corp, which is the ultimate successor to Bryant, makes a series of classified breakers (CL series) that are listed to fit in most or all of the panels mentioned above. They are expensive and I don't really know why they make them. I guess if the original panel label is missing they might be the most legit replacement breaker since they are almost certainly listed for any type in which they'll physically fit. Eaton does not make anything with a name including 'QP'