Should I change Queue Type of Parent Queue from PFIFO to SFQ when I do Priority in Child Queue? or I must do that ?
anyone ?
How we can possible know that? 
With same success you can ask if you should take an umbrella with you.
Bottom line - you need to provide information about your network configuration and priorities - is it latency, or less packet loss, or about problems that you need to solve.
And if it works OK - do not touch it.