Hello,
1) Moving large Column store BW Metadata and/or Column store Log tables to Slave: You can consider that but you should make sure that you perform proper house keeping to reduce size of log tables. You can refer to below document for more information:
http://scn.sap.com/docs/DOC-13132
2) Converting large Column store BW Metadata and/or Column store Log tables to Row stores on the Master: You should not do that without proper findings since master node system tables are stored on the master node. And meta data and transaction data is distributed across slave nodes. If you are worried about statistic tables, log tables, object metadata tables etc. then you can perform periodic house keeping tasks to keep the size of these type of tables in control.
Please also refer to SAP note 1855041 for more information.
Thanks
Sunny