I need to understand if there are any best practices or guiding principles to identify cubes and DSOs that need to be migrated to HANA-Optimised objects. Thanks.
Well you can convert all your InfoCubes to HANA Optimized Cubes as you get better loading and reporting performance and it makes Infocube design and maintenance simpler.
Check here for conversion of Infocube:
Generally you should migrate thoses DSOs to HANA Optimized DSOs that takes lot of time in DSO activation.
Check here for conversion of DSO:
To know more, check this blog: When should InfoCubes or DSOs be converted to the HANA-optimized versions?
Additionally, you should also read BW ON HANA Cookbook: