Did you ever have the stock 4.4 ROM on your phone? If you did, I'm not sure if you can load a stock Rogers 4.3 ROM via Odin because the stock 4.4 ROM may have altered the 4.3 bootloader. The stock Rogers 4.3 ROM from sammobile.com and the pre-rooted ROM on XDA will load a stock 4.3 bootloader if flashed via Odin. You could flash a stock ROM via mobile Odin which does not alter the bootloader.
Once you are on the 4.3 bootloader, you cannot downgrade the bootloader regardless of whether you do or do not have Knox.
If you are sure you never had the stock 4.4 ROM on your phone, you could use Odin to load a stock Rogers 4.3 ROM, unlock your phone, go back to a custom ROM.
When flashing a ROM or altering your phone's software, there is always the risk of bricking your phone. Just be prepared to deal with a possible brick.