• Wave function theory (WFT) methods: Because of the higher computational cost, our primary focus was on domain-based local pair natural orbital coupled cluster (DLPNO-CCSD) approaches. These methods offer a practical balance between computational efficiency and accuracy, often approaching the performance of traditional coupled cluster algorithms. To further improve the accuracy of DLPNO-CCSD methods, we also investigated the effect of incorporating explicit correlation through the use of the F12 corrections. • Composite methods: We combined the above approaches in various ways, for example using a lower-level geometry optimization/frequency calculation and improving the single-point energy with a higher-level method. Classical composite protocols (CBS-QB3, 70 G4 71 ) were also included. This approach tests whether high accuracy can be achieved cost-effectively through multi-level strategies.