In most of our previous work on GNRs and NGRs we have used DFT theory using the hybrid PBE0 functional (without "adjustable parameters), which was found more than adequate, especially for the energy gaps which were obtained with almost "chemical accuracy" in most (or all) cases considered. However, for the energetical ordering of the various spin states of the AGNRs, all (or most) DFT functionals (including the hybrid ones), for reasons we have already explained, misleadingly suggest open shell ground states, especially for larger AGNRs' lengths. On the other hand, introducing Moller-Plesset manybody perturbation theory (MP), even at the second order (MP2), reverses the results yielding a closed shell singlet ground state for all AGNRs (ZxA), which in the limit A=2 coincide with the series of peri-acenes (bisanthene for Z=3, peri-tetracene for Z=4, peripentacene for Z=5, etc.) we are examining here. Unfortunately, most of these (more recent) results about the true spin ground state are not well-known, leading to false conclusions about the true spin ground state of AGNRs (and alternant peri-acenes), even in seminal and important works of high impact. Since MP2 corrections have been proven the "philosopher's stone" for judging the true spin state, in the present study we combine MP2 (and higher order MP4) with (hybrid) density functional theory (DFT), in two ways: either by directly running MP2 (and higher 3 rd and 4 th orders, MP3, MP4), or by using double hybrid functionals which include by construction MP2 corrections. We use both. In all cases examined here the converged PBE0/6-311G(d,2p) geometries are used to run double hybrid DFT calculations (geometry optimizations and electronic structure) which include MP2 "corrections" using Grimme's B2PLYPD double-hybrid functional and the 6-311G(d,2p) basis set, as implemented in the Gaussian 28 programme package. Then, at the B2PLYPD/6-311G(d,2p) optimized geometries we run single point MP2-MP4, and in several cases CCSD(T), electronic structure calculations using the same 6-311G(d,2p) basis set, to optimize the energies (and energy differences). In addition for each structure and each candidate spin state (closed singlet, triplet, open singlet) the aromaticity patterns were calculated using NICS(1) aromaticity index, which has been proven sufficient and adequate for the purposes of such comparisons. For all calculations the Gaussian 27 program package was used and the results of the calculations were visualized using the GaussView 30 software.