Max smoothness suggested loadout from someone with high experience plz

Outside of using the new uber extremely demanding "RIFE AI" interpolation mode, the general jist is that a lower setting for a given option is smoother (e.g. Uniform is smoother than Adaptive and 23. Complicated is smoother than 13. Standard).

It must be noted that this "lower setting = smoother" does not apply to the options under the Miscellaneous options category nor does it apply to "Artifacts masking".  Also "Decrease Grid Step" honestly tends to be kind of placebo-level and I generally only find it useful if you have performance to spare.

The bigger problem is that smoother settings can also increase errors and artifacts and, outside of using the RIFE AI option, there's no universal best settings that balance smoothness and artifacts - you just need to try it yourself and see if the artifacting is acceptable to you or not.

However, there is one big universal way to increase smoothness and decrease artifacts, but it has nothing to do with SVP's own settings - it's all about making your screen refresh rate be a multiple of the source frame rate (e.g. if the video is 25fps, then a display refreshing at 50Hz is better than one that refreshes at 60Hz, same goes for 25fps--to-75Hz being better than 25fps--to->90Hz).  Custom resolutions may be necessary to achieve this but beware of your display skipping frames (note that TVs tend to be much more picky than PC displays), and even if you aren't using custom resolutions then I still highly recommend using MPC-HC's built-in "automatic resolution changer" or alternatively madVR's display modes functionality (do not use both however!); if you use mpv then use this mpv autospeedwin script.

Anyway, I'm a total frame rate junkie so I use quite intense interpolation settings, but I'll reference them as a starting point:

First off, set the interpolation multiplier / target framerate in SVP to To screen.

－ Frames interpolation mode: Uniform (max fluidity)
－ SVP shader: 23. Complicated
－ Artifacts masking: Disabled

－ Motion vectors precision: Half pixel
－ Motion vectors grid: 16 px. Average 0 for 1440p, 12 px. Average 2 for 1080p, 8 px. Small 0 for 720p, 6 px. Small 2 for 480p (none of my PCs are fast enough to interpolate 4k, so my settings max out at 1440p)
－ Decrease grid step: Disabled
－ Search radius: Large
－ Wide search: Strongest
－ Width of top coarse level: Large

－ Processing of scene changes: Blend adjacent frame
－ Duplicate frame removal: Do not remove
－ Rendering device: Do not change
－ Processing threads: Do not change

If you're watching 2D animation, then set "Processing of scene changes" to Repeat frame. If you're getting inadequate performance but your CPU usage isn't very high, then increase the "Processing threads" setting until you end up with full performance.

If artifacting is too great for your tastes, then the first step I suggest is changing "Search radius" to Average.  If artifacting is still too great, then either reduce the "SVP shader" to 13. Standard and/or keep reducing the "Motion vectors grid" setting until you are happy (the Standard shader setting is particularly useful if a video has moving thin lines); for 2D animation, avoid using 13. Standard and instead drop the "SVP shader" to 2. sharp (anime) if the artifacts from 23. Complicated are too much for you.