There might be a chance that you lose everything so I suggest not to change it. However, do what you want.
You should keep everything on all of the servers except for mcmmo and infection. We're still working on this.
I'm not sure why they keep saying this. I play with Optifine and turn off my animations and I'm perfectly fine. However if I turn my animations to normal and play on - Infection - OpPrison - Factions/OpFactions I lag a ton.
Can you fix the lag on hellblock? It's just insane, and I have lost so much iron and red stone to dying from issues associated with it.
Go to minecraft.net and sign in. When you sign in there should be a link on the page. Press it and it will re-direct you to a page where you change you ign. Here is a link to the page to help you speed up the process: https://help.mojang.com/customer/portal/articles/928638-minecraft-usernames NOTE: Changing your name will make you lose all your progress on some servers. I recommend waiting a bit for all the servers to associate with the name-changing. I plan on changing my name March 1st (My Bday)
https://help.mojang.com/customer/portal/articles/928638-minecraft-usernames This is a link that can help you change your in-game name. I hope it helped. PM me if you think you need a better explanation.