The question is - what is fair, and not to hard for you? I played EC more than 1,5k hours ant today i prefer vanilla settings. When i played it first, our server had harves x3, taming x5 and imprint stat scale multiplier x2, player weight x2 and costumized settings for beeding, so a rex needed about 8hrs mature time. We played on the island - the only map you can play every Extinction Core content without changing something. Dying multiple times is part of the gameplay. But at the end you have to find out by yourself what makes the game/mod enjoyable for you.

like the servers has, dino high lvls like 1200 or 600, the player reach lvl 300 or 600, and the engram points to learn everthing
those things

Creatures at lvl 1200? .... yea.. i mean, feel free to try, but Extinction Core is not optimized for that. There will be nothing you can call balancing. EC works best on wild dino lvl 120-150, people discussed balancing issues with raised difficulty multiple times. Player lvl has not to be modified if you play on maps were you can ascend. What you want to do sounds more like a fun server where game balancing and challenge take second place - what is ok, if you enjoy playing. I love Extinction core, but i think you might have more fun with mods like Pugnacia Dinos or Ark Eternal?

go play on Iark Extinction servers and see what i'm talking lol