I studied that Econo JIT is not optimized for the environment compiling the IL, different than the Normal JIT. Also, it doesn't create machine code cache for the next execution, which means every time the PE runs, the JIT compiles the IL into machine instructions again.
Pre-JIT is a contradiction in terms, since "JIT" means just-in-time, as in right before execution. If you precompile something, it is, by definition, not JIT-ing. The advantage is that you don't have the initial compilation delay that the JITter can introduce when an assembly or type is loaded for the first time in code.