From seed, most strains will have phenos that are high-CBD and some that are not (High CBD strain = strain with 4% CBD or more). Most strains I've grown have between 25-50% of the phenos displaying those characteristics. When looking for a keeper CBD pheno, I'm looking primarily for ratios (CBD:THC)...which can only be determined by lab testing.
The percentage of high-CBD phonos depends upon the strain. CBD-Crew makes claims of their new strains having 100% of the strains they offer being high-CBD, but I can't tell you if thats really the case or not. But once again, if you want specifics, you'll need to lab test.