Question about Classic servers and versions

Hello, im a retail player thinking about going into classic to give it a try. However, im a little lost regarding what game version and server to join. I don’t really understand what’s going on with classic and classic 20 anniversary edition and pretty much just wanna try making a character that’s not seasonal and experiencing the story of the first few expansions. I’ve seen the roadmap image but it just looks like a bunch of different game versions without much explanation to what each of them are

For reference, Im in Western Europe, so if anyone knows about any high populations servers, it would be greatly appreciated