When you say HUGE, what level of detail are you looking for? 1m, 10m, 100m, 1km, or something else per pixel?

When you say "Europe", what is your bounding box on the globe? Traditionally, the mainland of Europe runs from Spain in the South and West through Norway in the north and to the Ural Mountains in the East. It's a bit bigger if you include Iceland, Svalbard, and Crete, of course. That's a fair chunk of map to cover.

What is your desired map projection? That's an important question that relates to image size, especially in the northern reaches. Many existing maps are in some variant of Mercator or Equirectangular, which may or may not be suitable for what you want to show.

What software do you plan to use to work on your map? There are many maps out there that would let you annotate their base tiles and keep the underlying pand-and-zoom characteristics of the map, but it sounds like you have something else in mind. I ask because if your tools support a maximum image size of 8162 pixels, then you may need more than one map to get the level of detail that you're interested in.

How do you plan to present the map on YouTube? Screen capture from a browser?

https://www.naturalearthdata.com/ may or may not be useful to you, depending on your requirements for detail.

Any more information that you're willing to provide can help with the quality of advice that you receive.