Sager and Eurocom are two of many CLEVO-based laptops resellers. You can literally customize every aspect of your laptop. CPU, GPU, RAM, HDD, SSD, Network, and even the type of panel you'd like for your screen. And in many cases, you can also choose between different brands and models for each component. Which is of course pretty awesome for a laptop.
And regarding Eurocom, I had an exchange with one of their representatives who told me that opening the laptop to upgrade components yourself (even the screen panel) won't void the warranty. Of course, the components you'd be installing won't be covered under the original warranty, but all original components will continue to be covered if anything happens. It's good to know, as I've heard many stories from people who were told they voided their warranty by opening their laptop to simply upgrade/change the HDD or add more RAM.
And depending on the model you buy, some have pretty good upgrade paths (which is rare for laptops), that allow you to upgrade not only the regular components like HDD/SSD and RAM, but also CPU, GPU, Wi-Fi, screen panel, and so on, depending on the model.