I doubt any (server) Linux flavour today can run with 8MB RAM… Are you confusing it for bandwidth? That’s free upto 100GB if your apps are running in the Western half of the globe (docs).
You can check the dashboard to see the size of VMs allocated to your apps. If you’re comfortable using flyctl, then run flyctl scale show -a <app-name> (for Apps v1) and see what the output tells you.
Besides, if you intend to run proxies on Fly, see: What is included in $10/month plan? - #3 by eli