Eevee is used just to see the updates in real time right ?
so cycles can practically be used to render maybe a 30sec final animation right?
You certainly can, but know that Cycles Volumetrics take a long time to render! And Eevee Volumetrics are actually rather good.
If you have a super computer or use a renderfarm, maybe...
A simple calculation, if you were able to render 1 frame in 5 minutes, then that would be 12 frames per hour and with 24 frames per second, 1 second of animation would take you 2 hours and 30 seconds would take 60 hours! Just that you are aware...A renderfarm would of course be faster, but is that worth it?
Anyway, 30 seconds is quite long for a simple cloud animation rendered with a path tracer like Cycles
I was gonna detail this and add water and clouds
I wanted cycles because the render looks 100x better than Eevees
Go for it! You might consider rendering the main Scene in Cycles and the clouds in Eevee (in a separate Scene) and then composite them together to get the best of both worlds.
Eevee is used just to see the updates in real time right ?
No - Eevee is good enough to be used as a final render solution, especially when physical accuracy is less a priority. For example this entire animation was rendered with Eevee:
So Eevee has a lot of potential for stylized / cartoony stuff but it also can be used for realistic rendering as well.
so cycles can practically be used to render maybe a 30sec final animation right?
Unless you have a super-high end graphics card, you definitely will not be able to achieve 30-sec cloud renders with Cycles. The last lesson in this course I compare Eevee and Cycles render times and it's not pretty 😅