Deinterlace a DVD lossy using QTGMC hybrid?

[Selur]

Could someone explain what are the best settings.

No clue what would be considered to be the best settings. There are no settings which will always produce the best visual or lossless results. Normally folks want the pre- and post-processing QTGMC does. So in general I would recommend just to use the preset which matches your quality&speed needs.
If you really want to know more about the settings of QTGMC and how to preserve more of the original data best read http://avisynth.nl/index.php/QTGMC and the script https://github.com/Selur/VapoursynthScri...nc.py#L844 itself.
For more lossless content using the 'Lossless' option and lowering 'Sharpness' are usually a good idea.

I hope to upscale it and transfer to blu-ray

Then doubling the frame and upscaling make sure you use a Blu-ray compliant combination then. see: https://www.videohelp.com/hd

Is the quality better from doubled framerate or not?

If your content is interlaced then bobbing will preserve more motion data and potentially provide a more fluid output at the cost of doubling the frame count. If your content is not interplaced but telecined, do not use QTGMC. If your source is an NTSC DVD than it's probably not interlaced, but telecined. QTGMC on it's own is not suitable to be used on telecine content. (TIVCT+QTGMC, VIVITC+QTGMC, QTGMC+sRestore or just a IVTC method should be used then.)
-> Seeing that you do not know what you are doing:

• you should read up on what interlacing and telecine is, how to differenciate between them and how to deal with them.
  
• Hybrid might not be the right tool for you, since it's meant for users with more experience. Sure it can be used with others, but tools like MeGui and StaxRip are probably more suited since they are more starter friendly.
  

Cu Selur