For metrics you can see which ones do consume DDUs allowing you to rule out DSFM ones from consumption. You can do that 2 ways, either on the consumption page detailing DDU usage or using the builtin:billing.ddu.metrics.byMetric metric.
As for the logs, are you referring to the ones in the dt.system.events bucket?
Using the same method but for logs, it appears that when using classic logs, dsfm logs don't consume DDUs. The metric being builtin:billing.ddu.log.byDescription and then also the same info can be found on consumption page again. Using builtin:billing.ddu.log.byEntity you can also see where consumption comes from. I have some dsfm logs in my environment and they do not appear to contribute at all, neither showing in the consumption page or on the billing metrics.