Is there a way through Marketo to know if clicks are happening on mobile vs. desktop?
Here's on resource that might help you:
Build a Lead Performance Report with Mobile Platform Columns
If your question is about clicks i email, the "Cliked link in email has various constraints that may answer your question :
The "opened email" gives you the same possibilities, but it's about openings, not clicks.
Hope it helps,
If you're looking for even more in depth reporting, we've been experimenting with Litmus analytics lately. They give you some really nice dashboards for each email.
Here are some samples: