Thank you so much for detailed response. This clears my doubt.SInce you have not landed yet, I will take a hypothetical date and answer . Lest say you land on 01-Jan-2018. Then, between 01-Jan-2018 to 31-Dec-2023 you need to have 730 days or 2 years physical presence in Canada. After 31-Dec-2023 it is a 730 days or 2 years for any given 5 years. That means, after 31-Dec-2023, if IRCC examines a period from 01-May-2018 then they will examine 01-May-2018 and 30-April-2023. SO, after the first 5 years at any given point in time period there should be 730 days or 2 years physical presence in Canada to be considered as you having met the residency obligations.
It is however , not 0-5th year time period and 6th-10th year time period. It will be 0-5 and then it will be 1-6th year , 2-7th years and so on.
For Citizenship, as of now its 3 years physical presence in Canada. So, if you have 3 years in the first 5 years then you are eligible why go for the 6-10 years time frame. The physical presence in Canada need not be continuous except that it will be 3 years as compared to 2 years to maintain as PR.
So 2/5 to sustain PR and 3/5 to claim residency.