Arms throws are good for when you only have one hand-to-hand grip or a two-on-one grip (youre grabbing one of your opponents arms with both hands).
These throws are very hard for me to setup intentionally, usually you just have to see the opportunities as they come.

Seoi nage can be done with 2 on 1 grips or just 1 grip as long as you move your arms together.
Typically as i am turning in the direction of the arm im holding, i raise and then quickly pull down the opponents arms so they are tossed over my back.

Morote seoi nage is rare but the same but with 2 hand to hand grips.

yama arashi is like seoi nage only i am sweeping with my leg.

"head and arm drag" is what im calling a shoulder throw with a head grip plus the hand to hand grip.

idk if the different grips seems confusing but the replays all show a similar movement of the harsh pull on the arm which causes the opponent to follow and fall over.