Hi Osa,
I'm not currently on the Flame plan with any of my projects, so I won't take the survey - but, just anecdotally, what I find most confusing is the switch from Flame to Blaze:
Let's say I have an app that mostly relies on one aspect of Firebase (say, the Realtime Database), but manages to stay well below the limits for all other aspects (like Storage or Cloud Functions). While I'm on the Blaze plan, I get a certain amount of GB stored and GB downloaded, plus other stuff "as a bonus" for 25$/month. If my app grows and I need to switch to Blaze for just the Database aspects, even the same or less amount of GB stored (2GB = 10$, less than the 2.5GB included with Flame) and GB downloaded (20GB = 20$) will cost me more while at the same time losing (or having to pay for them) all the "boni".
I understand that this might become less important quickly as the app scales, but this still feels strange. In addition to that, I'd probably sleep better if, after switching to Blaze, I would be able to optionally set a limit for my monthly costs even if that meant that aspects of my app might stop working eventually.