On the Frigidaire DW, my parents had 2 models that were very similar to that one.
First one they left in a house that we moved out of in 77. Wash arm didn't have the mini-arm, but did have the middle tower. Was a decent machine for a portable.
After the move in 77, mom couldn't get the POS Tappan out of the house fast enough and replaced it with another Frigidaire. Difference between the first and second one- #2 had No Heat Dry option, the mini-arm, and it was a built-in. Racks were basically the same between the two machines. Was also a decent performer. I think it lasted about 12 yrs. roughly before she had to replace it.
On the Signature-
The dryer rack would sit inside the dryer when you set it for "No Tumble" and you laid what you were drying on the rack. the rack allowed for the heat from the dryer to circulate around the item being dried without it being tumbled. great idea for items that were very noisy when tumbled them but you wanted to dry them quietly.