I used the suntour suspension seat post with a cloud 9 seat.  The seat I have had on my last 3 ebikes its 5 years old and still going strong. I also put the tannus armor in the tires so i can run at a lower tire pressure. I usually run no more than 20psi in the snow i go down as low as 10psi currently i am at 15 psi for the winter.  That really helps with windy days because i can feel the tires grip when the wind tries to blow me sideways.  All things considered my ride is very comfortable

I have had a hard time finding one.  I am currently using a bag i got from amazon it has velcro tie downs.  I had to buy more velcro stripes and get creative but it works good now.  Rad just came out with hardshell boxes that i belive will fit on the rack and are compatible but its kinda pricey. The top box is like 159 or something and the hardshell panier is 199. My advice is to get creative and make your own style.