RE: Reinstalled W10 1511 --> 1607, problems with 2-finger-scroll
I don't know if I can help much but 1607 has been out for quite a while and another new build may be coming in the next few months. Hopefully, your system has received all the updates. The next time you reinstall, you are aware you can download the media from Microsoft and possibly Dell and have a later version to install.....
As far as I know, there is no touchpad driver from Dell. I did a clean Win 10 1607 install on a new drive and the touchpad seemed to behave the same as it did with the OEM install.
There are settings for the Touchpad in Settings-Devices- Mouse & Touchpad. You might check to see if any of those options help. I do not know if you have a "Precision" touchpad or not.
On my system, I find it is best to place the fingers on the pad prior to initiating movement. If I try to swipe it seems to delay the gesture.
I also have to be very careful not to allow the system to read a Tap movement since it seems just breathing on the touchpad can illicit a reaction.