Page Builder for Wordpress

[Paul]

Basically what we are looking for is that we must be able to customize our landing page and add new features if needed. And also looking for an option where a default theme will be provided and I will be able to customize it as per my own decision.

Oh, I completely understand your query. For good and premium themes look into 'Thrive Themes' and for the feature of default theme that you will be able to customize look into 'Divi Builder', its a pretty good one.