If you can create a list - parent child relationship between "Planning Product Name" and "Chain accy Planning Product Name" columns, then using Dependent drop down you can control by seeing one parent (based on the Planning Product Name column selection). This way you can control seeing one Parent name displaying in the list formatted line item column.
The simplest way to limit the view is to create a subset of the main list. You will need to create a subset for each incidence in which you wish to limit options. This approach will allow you users to see a limited view of the same list which will ensure downstream modelling is simpler.
An alternative is to use selective access and only provide write access to those list items required by each user. They will only be able to see those list items allocated to them when setting them up as a user.
When selecting which list items that are visible do not select the parent and only allow access to the child items at the hierarchy level required.
Test this approach by limiting your own access to a selection from the list. Be mindful of NOT turning off you admin rights as you will not be able to reverse the change.