The OINP and the EE are different. Follow the instructions for each application. In the EE, the maximum points you can get is for 3, years of work experience. As long as you provide the reference letters for the three years or more, for which you are claiming points, that is sufficient. For the remaining work experience, you will have to mention it in the personal history, for which you will not need reference letters.
As regards, OINP, you will have to list the work history for the last 10 years, as asked. You work history in your EE will match this, however, only the last 8 years will be in work history, the remaining will be in personal history. You will only be asked to provide references for the work experience you have mentioned in your work history.
Hope this helps and makes it clear.