This paper addresses optimizations of both power allocation (PA) and relay position (RP), PA-only, and RP-only in multihop relay networks under a generalized model of fading channels. By adopting a parameterized model of fading distributions in the high-signal-to-noise-ratio region, we formulate the optimization problems in a unified framework, which are applicable to most of fading channels and solved with the Lagrange multiplier method. The optimal solutions are derived in explicit forms that facilitate the analysis on the performance of multihop networks. The analysis shows that the diversity order of the end-to-end performance is governed by the hop with the maximum diversity order in the cases of the joint optimization of PA and RP and optimization of RP-only while it is governed by the hop with the minimum diversity order in the case of the optimization of PA-only. Henceforth, the optimization of RP, improving both the diversity order and coding gain, leverages the system performance more significantly than that of PA, improving only the coding gain. By improving the diversity order and coding gain simultaneously, the joint optimization of RP and PA shows the best performance.