It does need to reach that range of 3-5k for peak vanilla fun. It does get higher than 1.4k, but not enuff. Possible it could grow, but I currently have no reason to think it will.
1.14 is the blizzard classic client. This server is written on the original 1.12 client, so there's the addition of an emulator you need to run 1.14 on top of 1.12. Sugarproxy. 1.14 has updated graphics and would utilize entirely different addons. 1.12 is the old school, original vanilla client. All of my addons are 1.12 because I've been using it for years and years. If you skim through the help section of this server's discord, you'll see many issues with the 1.14 client. I have no idea if that is indicative of everyone's experience, but i do want to look into that. Here's a good post on 1.14 on this server, written before it opened I think. www.reddit.com/r/wowservers/comments/1dqgt5i/guide_how_to_play_112_vanilla_with_the_modern/
There are no 10k average peaks. I don't know where they got that number from, perhaps the previous realm? There are also no chinese, they are on a different server.