Install in few clicks, it will not take long than 1 minute.
Half of information is kept in json format, this allow to avoid an additions tables with couple of thousand of rows and big Join Query.
It work fine with more than 2000 products on shared hosting.
The CMS is builded on Laravel 5.7 one of the top secure framework at this time. Was care of all data what come from users.
Ecommercecms support theme and module, what allow to create the controllers and views and roots, direct in theme or module. If you will need an additional functionalities you can make them direct in theme or create a module. This give you the option to ask an developer to create a module for your needs without change core of WhatCMS.
The HTML and CSS its maximum optimized, but all depend the theme
The CMS keep the same structure as framework Model View Controller, to do changes will be enough knowledge of Laravel, you could create Controllers and Modules direct in your Theme or Module.
On Laravel website you could find all the documentation you need to do some changes or add additionals options
The Admin Panel it's well designed, this will minimize the time for training your customers