Started working full time on Implied status and got PGWP after 3 months. Can I use these 3 months for the Express Entry profile?

[thunderPharmD]

Dec.2019- PGWP applied
Mar.2020- Got PGWP
1. When is the best time to apply for PR?
2. I want to quit my current Job (by Jan.31.2021), is it safe (Assuming that I got 1-year experience for PR when 3 months of implied status is included)?