Stuff in sealed bags has been inside the bags long enough that there should be no risk. COVID RNA is detectable on metal surfaces for up to 72 hours but limited data suggests that live infectious virus does not survive that long. There are a couple of tests that are relevant to this question: 1) the RT PCR which detects the presence of viral RNA, but does not tell you if that RNA is in an infectious viral package; and 2) culture tests which attempt to actually grow the virus in vitro, and can quantify the amount of infectious virus (that would be a risk to you). As I said, there is very limited data available to answer the question, and in specific instances there is NO data available so you just have to be prudent.
Since there is no 'chain of custody' for assessing risk (how long ago was the package assembled, was the packer sick?, was the handling through the postal system 'clean'?, if handled by someone who is sick did they deposit a large viral load on the package contents?), it seems prudent to wipe down the outside of packages. I don't bother cleaning items inside in sealed plastic packing because the risk is probably close to zero. In any case, it makes sense to wash hands often and to avoid touching your face after opening mail and packages.