With the development of science and technology, people have higher and higher requirements for the capacity of network communication. Conventional single-mode single-core optical fibers have gradually approached the Shannon transmission limit of 100 Tbit/s. mULTICORE FIBER (MCF) based on Space Division Multiplexing (SDM) technology has good application prospects for the problem of upcoming capacity shrinkage. However, a specific issue related to MCFs is Inter-Core Crosstalk (ICXT) which can degrade signal quality and limit SDM performance significantly. In real MCF, due to the random perturbations and additional birefringence fluctuations, the ICXT changes randomly in the longitudinal direction. Therefore, approaches to estimate the ICXT are required to analyze the performance of an MCF transmission system. Coupled Mode Theory (CMT) and Coupled Power Theory (CPT) are common methods for studying the coupling characteristics of weakly coupled MCFs. In this paper, the CMT and CPT are optimized considering the influence of stochastic bending and twisting perturbations in the actual fiber laying process, and the ICXT estimation expression is obtained. For the CMT, due to the consideration of bending and twisting perturbations, the equivalent propagation constant in the Coupled Mode Equation (CME) is not constant, but the relationship related to the transmission distance, bending radius, and twisting rate. Therefore, it is impossible to obtain analytical expressions by directly solving the CMEs. The MCF can be divided into N segments by the segmentation method. In each segment, the distance is small enough so that its equivalent propagation constant and the incident power can be approximately regarded as a constant in weakly coupled MCFs. The final ICXT result is obtained by superimposing N sections of ICXT which is obtained by solving the CME in a short section. We call this model the optimized coupled mode theory model (OCMM). For the CPT, the local power coupled coefficient can be obtained by defining the equivalent propagation constant which contains the influence of bending and twisting perturbations. And the optimized average power coupled coefficient can be obtained by averaging the twisting rate. Finally, the crosstalk estimation expression can be obtained by substituting the optimized power coupled coefficient into the coupled power equation and solving it. We call this model the optimized Coupled Power Theory Model (OCPM). Simulations are carried out to compare the above two optimized models with discrete change models and experimental data. The simulation and experimental data are in good agreement. The OCMM results that ICXT as a function of the MCF length show an upward trend of oscillation along the results of the Discrete Change Model (DCM), in which the crosstalk cumulatively increases near the phase matching point and is almost unchanged near the non-phase matching point. Therefore, the OCMM can better reflect the fluctuation of the physical structure of the fiber, while the OCPM shows linear average crosstalk. In addition, the ICXT as a function of the bending radius in the actual homogeneous and actual inhomogeneous MCF is simulated, and the results of the two models are in good agreement. However, in the actual homogeneous MCF, the simulation results of OCPM and OCMM will be somewhat different. This is because OCPM is a simulated average crosstalk, so OCMM is more accurate in this case. In the actual non-homogeneous MCF, the simulation results of OCPM and OCMM are in good agreement. In this case, the calculation speed of OCPM will be faster. In summary, this paper derives optimized crosstalk estimation models based on CMT and CPT, respectively, and verifies the correctness and accuracy of the theoretical model through comparative studies of simulation and experiment. We can select suitable theoretical models for different actual situations.