Questions about new Internet Backup feature

Eero has announced the ability to use a mobile hotspot as backup if the ISP is down.  Some questions:

1. Can I configure eero to block all video streaming and gaming apps when on  backup?   It's a great feature but I have limited monthly high speed usage on my hotspot.   I have several Rokus and other things in the house that continue to use massive amounts of bandwidth even when nobody is present.  I can't switch the whole house to Backup on my hotspot unless I can stop those things from quickly using up all my monthly allotment.
2. Eero says I can configure up to 8 backup hotspots.  Will it use them all at the same time?  Will it do smart routing across all of them?  Or will it just use the first, unless it fails, then the next, etc?   
3. Can I get eero to use all my backup devices all the time to improve performance of certain apps?   Or will it only use them if the ISP is down?