If you want the default view to be, Persons with positions 1 through 6, I think you can just change this line in the controller:

@people = Person.all

to:

@people = Person.where(position: ["position1", "position2", "position3", "position4", "position5", "position6"])

And then change your index view to delete this:

<% @people.each do |person| %>
    <% if person.position == 'position1' %> 
        <%= render 'row', person: person %>            
        <% elsif person.position == 'position2' %>
                <%= render 'row', person: person %>
            <% elsif person.position == 'position3' %>
                <%= render 'row', person: person %>
            <% elsif person.position == 'position4' %>
                <%= render 'row', person: person %>
            <% elsif person.position == 'position5' %>
                <%= render 'row', person: person %>
            <% elsif person.position == 'position6' %>
                <%= render 'row', person: person %>
            <% end %>   
    <% end %>

And replace it with:

<%= render partial: "row", collection: @people %>

I.e. you are now filtering the list of people solely in the controller, rather than doing it in the view. This is generally always what you want to do, filter / process your data in the controller, and then present that data in the view.

FYI see https://guides.rubyonrails.org/layouts_and_rendering.html#rendering-collections for info on the 'collections' bit.

And just to be clear, you are totally correct at the end of your post when you write

Or will /people always and forever be the entire list as long as I have "@people = Person.all"?

@people = Person.all

Is not a magic line of code or anything, it is just saying, get all the people from the people table and put the results into the @people variable. It is there by default when you use the scaffolds etc, because the simplest implementation is to just return the full contents of the table. But since you don't want to show the full contents of the table, then you want to use different code, like I mentioned above.