In AEM 6.4, editable (dynamic) template, can we use inherited parsys feature (iparsys)? As we were able to do in static template earlier;
Yes, You can do that. It depends on your page component, whatever structure you'll define in page components will be available.
In most of the helpx documents they have used responsive grid but you can use iparsys in same way.
Why would you want to use Iparsy when you can set policies for an editable template.
please see this blog:
iParsys-like behavior with layout containers?
using policy you just allowing the components.