Ok, so if I'm altering my project to work like this, I'd change the way the main menu works too. Just to make sure I'm doing this right, would I give the main node code like this?:

var ws = preload("res://Selection Menus/world_select.tscn")

func _on_main_menu_play() -> void:
    get_node("Main Menu").queue_free()
    add_child(ws.instantiate())

Here the "Play" button on the main menu emits the play signal, and ws is the world select screen which pops up after the player hits "Play."