Cum kiss, cum swap, snowballing are all just different levels of the basic cum kiss.
A cum kiss is just when you kiss your partner with cum on/in her mouth. It could be the whole load, or it could be just the taste after she's swallowed. The amount matters less.
Cum swapping involves swapping the load from one mouth to another. The lips don't have to touch (drooling), so it's not technically a "kiss".
Snowballing involves multiple swapping until the load turns into a big frothy mess. Extreme cum swapping.
This video shows all 3. See at the 5:00 mark for a great example of the snowball effect.
https://www.xvideos.com/video84805/s...g_with_a_spoon