I could achieve this i.e. creating a list's NewForm named CustomNewForm.aspx setting it as Default NewForm and editing it in advanced mode to add a script code which redirects to CustomForm.aspx Page using code
window.location.href = "/sites/<Site Collection Name>/SitePages/CustomForm.aspx"
Using SharePoint Designer but as per deployment is concerned I need to achieve this using Powershell only. Is there a way to do the above two steps using Powershell or is there a better solution to achieve the task of mainly to redirect to CustomForm Page (The CustomForm.aspx page has custom UI and consist of jsom code to create a new ListItem) for creating new item in the list and making it available on the click of New item button.