Are you investigating the trees of your matches? Or are you mostly grouping?
If the group has a good amount of matches, it's often not difficult to find common ancestors among the matches. I open up dead-end ancestors of people in each tree and press the [Search] button for them. Typically they occur in another tree with more ancestors. Otherwise you can look them up in records. So the unknown ones I will label based on the common ancestors in the trees, such as:
Jones of Llanbrynmair
Dodd-Carter of Suffolk
With all the groups I don't know what the link is, I then put them into groups, where I think they probably have a connection, like so:

When you have groups of matches when the largest match is not greater than about 32cM (not sure of the exact threshold, might be higher), those tend to be more distant with common ancestors more in the window 1700-1730. That takes you back to about 6X GGPs, of which you have 128. So you'd need to have a pretty good idea of who those 128 are to make sense of your DNA matches, and I don't think many of us have close to that.
So, I've not been able to determine a relationship between most of my small clusters, which is in part due to remaining NPE gaps; otherwise due to inadequate records.
A key aspect is how far back shared ancestors in a cluster are. In my experience they always range from MRCAs in the window 1800-1660; typically more towards the former. If a cluster has matches that go back further on a line, then you can see there are no NPEs on that line.
You can have other clusters where you can only find MRCAs going back to 1800, and not know how they connect to you. So the common ancestor with you may be three or even four generations earlier. So when you don't know all your 6X GGPs and you then have to have a reliable tree for the 1700s of multiple lines of ancestry - most of which are not shared, it becomes cumbersome. If you are lucky there is an obvious surname link, but that occurs in the minority of cases.
As an example, see the char above where I have clusters for York and Ward-Wright. I found marriages between Yorks and Wards; and Wrights. However, since I don't know where in my tree that fits in, it's just a mystery.
There's also the possibility NPEs mean that actual paper trial in the cluster are false. There are so many variable that make DNA a delicate art. One ancestor was married in India and listed as being from an orphanage. Her surname was Nash and I've found nothing from DNA that connects to that surname. So I lean to that not being her birth surname. I've got a few clusters I know fit onto her general line, but I don't know which, if any, relate to her. One has MRCAs from about 1770. With no further generations. For all I know one of them was actually an NPE deposit from an unknown ancestor.
When I first began, with no knowledge, I clustered too fervently and made clusters that don't actually exist. This is done by clustering when there are not enough common matches. I tend to only put someone in a cluster if they share at least three matches in a cluster. If you add everyone who just matches one, you will end up with giant clusters with no common thread.
Another mistake I made is thinking that if I could not find DNA matches on a line, then it's probably due to an NPE. I felt pretty certain that two of my lines were NPEs. However, after more time and knowledge, I found that matches were just hidden away. Specifically almost all of the matches on one line also matched another line independently. Then the other cluster is just small and very diffuse; while still having matches with MRCAs back to c 1720.
So there's a very large amount of time and moderate knowledge that allows you to make the most of the matches. I was going through some matches a few days ago when after a lot of digging I found MRCAs from c 1715, some of which were from matches I'd written off. So there is always the possibility of finding more, but mostly I don't know how I am related to these people.