I use Bigger Settlements and the Sandbox mod you mentioned along the thread, if I don't get too much far from the usual borders it works fine. Places where I had to assign manually the settlers have been some stores on the second floor of the highway in Zimonja (yeah it goes that far Bigger Settlement) while on the rocks just outside the border the industrial plots works really good. Same at Nordhagen, a couple of plots in water far from the seaside I had to assign manually, the rest works automatically.
EDIT: the HUD works almost everywhere, sometimes I get it far outside of a settlement: example moving from Red Rocket to Sanctuary it never goes away, it just changes the values.
EDIT: the HUD works almost everywhere, sometimes I get it far outside of a settlement: example moving from Red Rocket to Sanctuary it never goes away, it just changes the values.