The first episode was an hour, but eps 2 and 3 were less, around 40-50 mins. (I haven't watched 4-8 yet.) So there was some loss of runtime, and I understand the need to change some things to make up that time. However, (and granted I'm only three eps in) I doesn't feel like the changes that were made were made strictly for runtime reasons.
Gran-Gran giving Katara the scroll instead of her stealing it, yeah, I see that being a time saver. The overall change in Katara's personality? Not so much.
In some different countries, WhatsApp is how people conduct business. I am anti WhatsApp in my regular life, but I used it with a VOIP number when I was traveling abroad.
It's one thing to tell your friends and family you use Signal, you can't tell literally every business. Well, you can, they just won't to do business with you.