@Mireille Beumer -

a lot depends on the devices which your participants will be using to collaborate. If they are on a smartphone for example, size and scale will be very different than on a large screen monitor. 

In general, what I've done is to let the typeface of my text dictate the size of the frames I use and since frames are the basis for exporting to a PDF file, I try to keep my frames all roughly the same size unless an activity requires a significantly larger or smaller frame.

I’ve found that a 24 size typeface works fairly well for me as a default.

Kiron

Thanks a lot @Kiron Bondale 

And what dimensions do you use for your frames, when you have more then 1 activity (and every frame describes one activity)?
Do you use the frame which has the dimensions of your screen? (you can choose this dimension in the frame lay out). 

Mireille

@Mireille Beumer -

I’ve never used one of the standard frame sizes - in general, mine are usually portrait mode and would fit within most reasonable laptop screen resolutions at roughly 80% zoom ratio.

Here’s a screenshot from one of my course boards. As you can see, the four discussion/brainstorming-type frames are all more or less the same size, whereas I went with a larger size for a more elaborate activity which involved categorizing items into four groups.

You are great, thanks a lot @Kiron Bondale !!