The load and go is a 40 load dispense on the WFW6620. It is a dispenser that sits inside the bottom pull out drawer. I believe it is smaller on the 5620.
The 5620 has Sanitize with Oxi. The 6620 and 8620 just says Sanitize. I do believe the Energy sticker hs more KWH on the 6620 than the 5620. I'll opt for one that uses more energy indicating the heater is used in more cycles.
The WFW560CHW doesn't have a steam cycle. The WFW5620HW has the regular sanitize and a steam clean option. The only difference between this and the 6620 is that the 5620 has a smaller load and go dispenser.