One of the best ways that you can add the scroll effect in WordPress is that you need to use a plugin. Why? Because adding in the scroll effect is a very complex process and it can be very challenging to do without making a mistake on a website.
Making a coding mistake can be very challenging to repair. You would need to have a backup to ensure that your website is safe should something happen.
Another factor is that by using a plugin, you can get support from the developers. This means that if there is a problem, then you might have some backup to solve it.
There are numerous scroll effects available. However, there are some themes, like Soledad that can help you create a scroll effect when the user moves down the page. This means that you don’t need a plugin.
Plugins can be costly or they can be free. The problem with a free plugin is that the developers don’t have any incentive to help you should something go wrong.