  The recently discovered AV$_{3}$Sb$_{5}$ (A = K, Rb, Cs) compounds have
garnered intense attention in the scientific community due to their unique
characteristics as kagome superconductors coexisting with a charge density wave
(CDW) order. To comprehend the electronic properties of this system, it is
essential to understand the lattice distortions associated with the CDW order
and the ground state electronic behavior. Here, we comprehensively examine the
Fermi surface by a combination of angle-dependent torque magnetometry and
density functional theory calculations. We observe magnetic breakdown in the de
Haas-van Alphen oscillations under high magnetic fields. Additionally, by
examining the angular and temperature variations in quantum oscillation
frequencies, we gain insight into the evolution of the three-dimensional like
Fermi surfaces and the cyclotron masses of the orbits, which are consistent
with weak electron-phonon coupling. Notably, further comparisons indicate that
the 2$\times$2$\times$2 Star-of-David (SoD) distortion is more compatible with
both high frequency data above 1000\,T and low frequency data below 500\,T,
while the 2$\times$2$\times$2 Tri-Hexagonal (TrH) distortion aligns well with
experimental data at mid frequencies. This finding implies the inherent
coexistence of both TrH and SoD 2$\times$2$\times$2 patterns within the CDW
order. These observations provide key insights into the interplay among
effective electronic dimensionality, CDW state, and superconductivity.
