The paper investigates the mass spectrum of S-wave fully heavy tetraquark systems ($Q\bar{Q}\bar{Q}\bar{Q}$, where $Q = c, b$) 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 are those that cannot be composed of two S-wave ground heavy quarkonia. The authors incorporate both molecular dimeson and compact diquark-antidiquark spatial correlations to discern the actual configurations of the states. They use the Gaussian expansion method to solve the four-body Schrödinger equation and the complex scaling method to identify resonant states. The mass spectra from the three models qualitatively agree with each other. Several resonant states with $J^{PC} = 0^{++}, 1^{++}, 2^{++}, 1^{++}$ are obtained in the mass region (6.92, 7.30) GeV, some of which are good candidates for the experimentally observed $X(6900)$ and $X(7200)$. Several exotic C-parity zero-width states with $J^{PC} = 0^{++}$ and $2^{++}$ are also found. These zero-width states have no corresponding S-wave diquarkonium threshold and can only decay strongly to final states with P-wave quarkonia. The paper discusses the spatial structures of the tetraquark states and compares the results with previous studies.The paper investigates the mass spectrum of S-wave fully heavy tetraquark systems ($Q\bar{Q}\bar{Q}\bar{Q}$, where $Q = c, b$) 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 are those that cannot be composed of two S-wave ground heavy quarkonia. The authors incorporate both molecular dimeson and compact diquark-antidiquark spatial correlations to discern the actual configurations of the states. They use the Gaussian expansion method to solve the four-body Schrödinger equation and the complex scaling method to identify resonant states. The mass spectra from the three models qualitatively agree with each other. Several resonant states with $J^{PC} = 0^{++}, 1^{++}, 2^{++}, 1^{++}$ are obtained in the mass region (6.92, 7.30) GeV, some of which are good candidates for the experimentally observed $X(6900)$ and $X(7200)$. Several exotic C-parity zero-width states with $J^{PC} = 0^{++}$ and $2^{++}$ are also found. These zero-width states have no corresponding S-wave diquarkonium threshold and can only decay strongly to final states with P-wave quarkonia. The paper discusses the spatial structures of the tetraquark states and compares the results with previous studies.