No that is not how related data fields work in relation to performance and loading of data within an RG. It has been falsely presented over the years on the forum with few being able to correct the false assertions.
When using an RG to load all Accounts, any related fields will be treated only as text and load only the unique IDs of those related things, so the list of lines, employees, and phones will just show as unique IDs for each item within those lists, not the entire set of data fields for each type, so if for example on the employee data type you have a dozen fields such as name_first, name_last etc. those fields are not part of the data load. Anybody who states otherwise is speaking from an uninformed perspective. I’ve posted on this in the past and quoted Bubble support to give the answer ‘from the horses mouth’.
However, if any element within the repeating group, such as a text element, uses an expression to reference any field from a related field (ie: current cell’s Accounts employees first item name_first), then All data fields of the related type will be part of the data load…so, that brings up a best practice to follow when wishing to show related items like that, especially when it may just be one or two fields from the related type, is to on the type (in this example Accounts) have a field for that related field (so have a text field that would be employees name_first on the Account data type) so that you can show that value in the RG without incurring the slowdown incurred from having to load All the fields of the related type.
Depends on you in this situation, since both directions of relatedness for the employee and account is a list (ie: each employee has multiple accounts and each account has multiple employees)…just think about the way in which this data will be used by the app users to make the decision. Whichever list is expected to be smaller (will an employee have more accounts or will an account have more employees), put the related field as a list.
On the line data type put a related field to Account and field for phone
You don’t mention if anything will have multiple queues, so I assume there is not…so, on the queue data type put a field of Account, since one queue will have only one account presumably.
There would be no reason for this based on the description you gave as it doesn’t look like accounts have lines, but instead accounts have employees and employees have multiple lines, so there is not direct relationship between an account and a line, so you put onto the employee data type the line as a list field
Is there actually a relationship between accounts and lines?