Aaaaaaaahhhh this was great, Rebecca! As a fellow anxiety-haver I totally understood this, even though I didn’t have the same trepidation going into Breath of the Wild. In my case, I found the game not pressuring you to meet the main objectives constantly was refreshing, as it allowed me to set my own pace, but I see how overwhelming its sheer scale and numbers can be.
I think the only open world game to trigger similar anxiety was Fallout 4, because certain settlement quests—i.e. the only aspect of that game I really cared about—were timed. I coped by straight-up avoiding Preston so he wouldn’t give me any more missions and just building up my base defences as much as possible.