As far as I understand a collation is used for sorting/ordering of strings and case sensitivity. I would expect any of these collations to handle common characters the same way, but they may have different rules about how to order some of the extended characters.
My guess is that the only thing that may change if you use a different collation is that a list of user ids or sets could end up sorted in a different order if there were exotic characters in it. Nothing in WW depends on these sortings so at worst things would be displayed in a different order than before.
If we're going to set a default I would suggest utf8mb4_unicode_ci. The fact that it's older means that it is more likely to be available on any given system, whereas the newer ones may be too recent for some existing servers.