This has nothing to do with shader rendering. Your shaders are being recompiled which can indeed take a lot of time. Making lots of config changes that relate to rendering will often trigger a recompile of the existing shader library. You should therefore consider to evaluate settings in a separate, lightweight project that doesn’t require a large amount of shaders to be recompiled whenever you switch a setting.
Especially importing packages from the marketplace, which often feature a whole library of assets, will lead to an immediate, large increase in shader permutations in your project. All of the shaders in your project’s library, not just the ones that are currently in-use, will then be recompiled every time the config is updated with any settings that influence them.