Im not sure i understand what you mean by percentage of pH and PPM? Suitable ranges?
If you’re in only peat, I’d be treating it as soilless - no lower than 5.5 pH, wouldn’t go above 6.3 for early stage.
Depending on your nutrients your using, and if you’re using RO water or not
you’ll probably wanna be around 0.4- 0.8 EC (200-400 PPM) the first couple weeks of growth. Much of the nutrients needed for starting seedlings is within the seed itself.