There's nothing magical about level 20 you're right.

you just gotta have RNGesus on your side...

New players? Which new players? This isn't a thread to do with new players.

If you wanna be specific at level 20 you have the chance that 45 out of the 145 pokemon available will spawn in at 1k cp or higher.

At level 30 you have the chance that 108 out of the 125 pokemon available will spawn at 1k cp or higher.

When do 1000+ Pokemon start showing up?

So to answering OPs actual question at level 12 you have a chance of finding a maxed Dragonite for your level which would be 1050 cp. Only pokemon to go above 1kcp at level 12.

Level 13 you'd have a chance of finding a Snorlax maxed out at 1011/1012 cp. Only pokemon to go above 1k cp at level 13.

Level 14 you'd have a chance of bumping into an Arcanine maxed at 1044 cp, Lapras maxed at 1043 cp and Exeggutor maxed at 1034 cp.

Level 15 you'd have a chance of running into Vaporeon maxed at 1056 cp and Gyarados maxed out at 1008 cp.

List goes on with each level up to 30 of course but at level 20 you got access to 47 of the 108 pokemon that can spawn over 1k cp in the wild.