How much isopropanol is effective but safe for viny?

Only my opinion. And I may be wrong.

The questions really boil down to what bad stuff is in the grooves and what will be remove it. The most likely foreign materials would be dirt, dust, oils. Maybe some grease. It ends up that Isopropanol is not a very good solvent. A weak solution of distilled water with a dish washing liquid, like Dawn, would seem a good solvent for this kind of material. Maybe only a drop or two in a quart of distilled water.  Thorough rinsing would be necessary. Very thorough. That kind of residue from a cleaning solution like that is probably not something very beneficial to a stylus or cantilever.

But I may be wrong. It might clean but leave a residue very difficult to remove.

@boxer12

I use Triton X-100. Photo Flo is also good.

 https://www.amazon.com/Triton-X-100-Surfactant-500ml-Purity/dp/B009RZZB76/ref=sr_1_1_sspa?ie=UTF8&am...

I think I would limit the definition of a surfactant to a substance that reduces the surface tension of a liquid in which it is diluted, in this case of water.  This allows the water to be "wetter", to penetrate better.  Whether this also results in faster drying may be true, but I am not so sure it's a good thing, if so.  If water plus surfactant (usually a nonionic detergent) dries, then it leaves a residue.  In addition to isopropanol, my RCM concoction also includes a few drops of surfactant per gallon or so, and I usually use Tween20 or Triton X100.  (I think Dawn is fine in this application, too.) But I always rinse with pure distilled water to avoid leaving a residue.  My results have been better since I added the distilled water rinse cycle.

My solution is distilled water with about 10% isopropyl and a drop of dish detergent. This is used with a very inexpensive cleaning machine. I wipe with a microfiber cloth until nearly dry.

Stubborn records, the ones which still have a lots of pops and clicks, I use a lint removal brush, a drop of detergent on the record and scrub with the solution above which creates lots of sudsing.  Then rinse under hot tap water and dry.  Several unplayable records have been recovered to play as "very good" to "very good plus" after scrubbing.  I have several records purchased as "very scratched" for between $0.05 and $0.95 which play as "very good plus".... amazed me.

I don't remember what it was, but I think there was some question about using Photo-flo for cleaning LPs.  Anyway, something I read did cause me to stop using it about 10 or more years ago, in favor of Tween20 or Triton X100, or even Dawn.