@nyajigon22 Hey mate! As @Heliosurge has mentioned already, the Smart Smoothing feature creates less GPU load by only rendering half (50%) of the original framerate, and then somehow interpolating every second frame back to full 90fps. This makes it less demanding for the GPU and thats basically the reason why Smart Smoothing exists.
To render 45fps your GPU only needs to work at 50% maybe (depending on game of course). Without Smart Smoothing, to render full 90fps, your GPU needs maybe 100% (or more) and while the actual GPU usage often doesnt exceed 80-90% in VR games, thats why you got frame drops. So just use Smart Smoothing, and you will get a smoother experience.
Also, Smart Smoothing gives you a lot of extra headroom for the GPU (as its only running at arounmd 50%). With Smart Smoothing enabled, to get some higher GPU usage, you can increase the graphics quality, PiTool render quality or SteamVR supersampling a bit and still maintain a stable 45->90fps image. If you increase the PiTool render quality from 1.0 to lets say 1.25 or 1.5, you will for sure get a higher GPU load, maybe 60-80%. So tweak a little and try to find the best balance. With the new PiTool version, you can create profiles for each game which is awesome
As for ghosting/artifacts, yes SmartSmoothing is still not perfect and will introduce some of these minor issues. In racing and flight sims its not that noticeable and most people wont bother, but in FPS games like Skyrim it could get a bit more distracting. So use Smart Smoothing for your sims, and maybe only in other games that really needs it.