My name is Hal, and I'm one of the admins of the Breadcrumbs Group, which also runs a whitelisted Minecraft 1.12 server! The group has been around in various iterations since 2013, but we just started a new map yesterday. Our rules are pretty straightforward...
No Griefing - This rule is pretty much self-explanatory. Pranks that do not involve uncontrolled fire, lava, explosives, and anything generally destructive are alright, however.
No Bullying - There's a thin line between joking with someone and bullying them. Jokes are wonderful, but sometimes they can be taken too far.
No Hacking - Clients that provide any unfair advantage over other players are not allowed.
No Stealing - This community is being built on trust, so we expect players to not steal from one another.
Keep the World Looking Nice - If a creeper blows up; properly fill the hole. Do not leave floating treetops, pillars, etc.
We have a very simple application, which can be found here. We like well-written applications, as that to us is a sign of maturity more than age! We do use Discord as our main form of communication. If you don't have Discord, sign up and download it here. We also play more than just Minecraft, including games such as Overwatch, Civilization V, GTA V, and others.