First all thank you for doing this.
Information is important as well as experiments like this not just for the community here, anyone seeking to work on a low budget can make very good use of these information here.

My very first pick will be that fire 8 tablets, So long as people can download the necessary apps and be able to access hive, that's plus for it. The camera and sound system been good makes it my first pick. Hive most times attributes your quality contents to what can be seen, having a good camera to take some quality pictures that will go with ones blog will be an added advantage here on hive.

I won't go for the priton7, it has already off me with the poor camera and sound quality. Video contents are now a trending thing in hive and commoners who have no writing skills can make good will desire a camera to make video contents of their talents, be it singing or craft.

As for the service smartphone, well I like that it had all the qualities we wanted but honestly no body would appreciate a tiny mobile phone they will have to stretch their eyes to blog with. It will wear anyone out and make people loss interest.

For the Chromecast, that will be like creating a cybercafe kind of setting since one will be needing am arrangements of TV sets and a charging spot for the item.
People cannot have access to it in their homes unless they visit the cafe.The cafe may only run during the day time and night blogging will restricted for some. Night blogging is convenient when you have a mobile device of your own, people can run their other Jobs or side hustles during the day and be able to create contents at night.

But on another note having this choice of day blogging when you have no options is a good one. And a good place to bring people together like a play station.

I leave to decide what's best as I have just giving my personal opinions regarding each.