You don’t need to buy a plugin.
For mega menu. Go to WordPress admin -> Appearance -> Menu
Drag a custom link to the menu, then dropdown to expand it.
You will see a checkbox that says “Enable Theme4Press Mega Menu”.
Check it and select the number of columns, then save the menu.
After you save it, start dragging custom link to be it’s sub menu and you will be able to see the select for widgets.
In Alora theme, you can use different templates such as full width and 100% width template.
The is also page option to select a full width. Or custom css.