VideoProc

tl;dr [review written from FPS conversion perspecive] worth checking out, especially with fully functional (just video time limit) trial

• it supports exotic formats on input (mkv, no audio track, non-typical res, quirky x265 settings).
• it utilizes even my ancient GPU (R5 240). + Rather fast 0 results are meh - not great, not bad.

• Doesn't have compensation for rolling shutter, so dynamic videos recorded with DSLR after slow motion looks like poked gelato. 0 a lot of motion blur, but that could be because video was very bad.

• Free test version allows you to process up to 5 minutes of video (with a slight nagging - sometimes message box asking you to buy full version and "continue" button appears after 1-2 sec) and doesn't add watermark, so you can test how it fits you without hassle and even share results with friends.
• It's very easy, even your grandma will be able to use it.

• It comes with a price - no much settings, you can choose between two output formats (H264 and ~5) both with 4 quality settings - no customization, except "GOP" - not even defined if it's max GOP or min GOP
• It doesn't allow you to change framerate to any. Even official video support tells that to get 25x you need to encode to 5x, then again 5x - without lossless output, that's not good.