  We calculate the mass spectrum of the S-wave fully heavy tetraquark systems $
QQ\bar Q\bar Q~(Q=c,b) $ with both normal $ (J^{PC}=0^{++},1^{+-},2^{++}) $ and
exotic $ (J^{PC}=0^{+-},1^{++},2^{+-}) $ C-parities using three different quark
potential models (AL1, AP1, BGS). The exotic C-parity systems refer to the ones
that cannot be composed of two S-wave ground heavy quarkonia. We incorporate
the molecular dimeson and compact diquark-antidiquark spatial correlations
simultaneously, thereby discerning the actual configurations of the states. We
employ the Gaussian expansion method to solve the four-body Schr\"odinger
equation, and the complex scaling method to identify the resonant states. The
mass spectra in three different models qualitatively agree with each other. We
obtain several resonant states with $ J^{PC} = 0^{++}, 1^{+-}, 2^{++}, 1^{++} $
in the mass region $(6.92,7.30)\, \mathrm{GeV}$, some of which are good
candidates of the experimentally observed $X(6900)$ and $X(7200)$. We also
obtain several exotic C-parity zero-width states with $ J^{PC}=0^{+-} $ and $
2^{+-} $. These zero-width states have no corresponding S-wave diquarkonium
threshold and can only decay strongly to final states with P-wave quarkonia.
With the notation $T_{4Q,J(C)}(M)$, we deduce from the root mean square radii
that the $ X(7200) $ candidates $ T_{4c,0(+)}(7173), T_{4c,2(+)}(7214) $ and
the state $ T_{4c,1(-)}(7191) $ look like molecular states although most of the
resonant and zero-width states are compact states.
