is block chain driver good for this miner or old crimson drivers??
You can use any driver with this miner... The latest 12.6 version works with the new API of "amd blockchain beta" driver, however there may be some issues with voltages and stuff... so if you have older polaris cards you may opt for something like 16.11.4 with no bios sig check and watttool fully working
That is right. I use the old drivers such as 15.12 or 16.9.2 for ZEC mining.