Since the (re)discovery of giant magnetoimpedance (GMI) effect in soft ferromagnetic (SFM) materials, it has attracted much attention due to its remarkable advantages for the development of high-sensitive magnetic field sensors. Unlike giant magnetoresistance (GMR), the origin of GMI can be understood in the framework of the classical EM theory, i.e., the tendency of an ac current distributed within a magnetic conductor in accordance with the skin effect. The GMI phenomenon has been reported in amorphous wires/ribbons, glass-coated microwires, thin-films, and composite wires. Although MI behavior in SFM Permalloy (Py) thin films deposited on various substrates has been extensively investigated, they present significant differences. Further, the study of hybrid structures is important because GMI sensors in modern consumer devices require the development of thin-film “miniature GMI sensors” compatible with semiconductor electronics. Py (Ni80Fe20) films deposited on n-type Si(100) exhibit maximum MI (MImax) ~20% at a frequency (fmax) ~50 MHz with field sensitivity 18% Oe-1, which is a deviation from other reports. The pertinent question are: what role does substrate play in controlling MImax and fmax? Is it possible to tune the fmax value by choosing an appropriate (conducting/semiconducting/insulating) substrate? How does MImax and fmax change with the film and substrate thickness? How does substrate (planar or cylindrical) geometry and induced stress effect the GMI character? Whether it is possible to numerically simulate these results by using phenomenological models? To unravel some of these issues and to propose a viable model that can explain observed unusual features, a systematic magnetic and MI studies have been carried out on planar, cylindrical, and sandwich structures. Electrodeposited NiFe film directly on to semiconducting (ITO/glass) substrate and it is shown that the MImax and - fmax can be controlled by varying the film thickness and attributed to variations in skin effect. At lower frequencies negative MR contribution is dominant. Numerical simulations provided insight into magnetic parameters and enabled us to extract the permeability from MI data. We also showed that induced stresses during electrodeposition significantly reduce the magnitude of GMI due to magnetoelastic effects. Interestingly the non-magnetic core wire and magnetic shell geometry provide higher GMI values and sensitivity. Investigated the effect of interface layer thickness in the sandwich structure films to enhance the MI and magnetic field sensitivity of the material.