@Greg27
the group members in the code meant to be service accounts that should be excluded from the combobox.
i assume your combobox does not allow multiple selection.
when you make any changes, you need to make sure that toggle 'Allow searching' is ON on the right settings panel ( as it gets off sometimes as code changes).
or
yes, you can place all combobox accounts into a single azure group, get group members into a collection in powerapps and point combobox items (source) to that collection to avoid expensive http calls.
// get accounts for combobox
button.OnSelect =
ClearCollect(colAzureGr, Office365Groups.ListGroupMembers("YourSecurityGroupGUID").value);
ComboBox.Items = colAzureGr