I want to build a pppoe-server from rb1200 with radius authentication and rate-limits. Rate-Limits will pass radius server with radius attributes. What settings need to change to get the best performance?

For best performance, do not send rate limits per-user, as this will create a lot of simple queues on your RB, slowing it down significantly.
Instead, create PCQ Queues on your RB matching your services (e.g. Queues for 1024/256 kbit service, another one for 2048/512 kbit service),
and have them match address-lists. Then, use the mikrotik-address-list radius attribute to dynamically add your users to these queues.

Hello,
I'm try implement this like this:
http://forum.mikrotik.com/viewtopic.php ... OE#p308767

Have I use limit-at on size of users?
For example: I have two pcq for 1Mb/512k. If Ihave 30 users where site the 30Mb?