Awesome to get all this feedback thanks so much everyone! You're definitely describing some of the pain points I've been feeling with trying to keep instagram updated!
I had signed up initially with HootSuite's free plan which maxes out at 3 accounts (which most of us are probably good with say using Instagram, FB and maybe toss in Pinterest). I'll check out Later.com!
I did look at the Instagram app for win10 (I've got a windows machine at home) but crazily enough it doesn't give me the option to post a photo. I can RESPOND to a photo, but not post, and then when I researched it a bunch of people said that feature was missing, but others said it was there, so it was super confusing.