Plan upgrade

I'm about to launch a game. Before launching, I'd like to study the realtime plans.
Currently I'm using 20ccu (free) plan. Photon says 'We recommend you to upgrade before using it in production.'
For now, I'm not sure how many users I have. Then should I just upgrade my current plan to 100 ccu, when I need it?
Is it fast and easy to upgrade to the higher plans? I mean I am wondering if I can do it without any loss.
Thank you in advance for enlightening me.