For rennet add after culture ripening, you're looking for a delta pH of .1. So, for example, from 6.6 to around 6.5, rennet.
Flocculation multiplier of 4x
Whey drain pH of 6.0-6.2.
Cut into pieces for brining at 5.4-5.5 for a firm style. Else, leave in molds to acidify until 4.5-4.8 for normal styles.
That is for a firmer style. For a softer style, drain pH is on the higher end (6.2), and don't cook as long, and let it drain in the molds to acidify before brining.
End pH should be at 4.5 if you like a sour feta to 4.9 if you like a creamier one that's not as crumbly. Yes, lipase is a must for flavor.