Intel AC 7260 wifi performance problems

Hi all.  I have a 2014 vintage Latitude E5440 with an Intel AC 7260 network adapter.  I am running the most updated version of Windows 10 pro.  Over the past year or two, the wireless adapter basically shuts off and I have to reset the adapter to establish a new connection.  I have read many posts in this forum and have tried most of the usual fixes.  I have not had much luck.  Here is what I have tried so far.  These settings reduce the problem, but it won't go away.

I rolled-back the 7260 driver to a 2014 version.  Newer driver versions drop all the time - the older driver is more stable, but not perfect.  I have not allowed the adapter to be turned off to save power.  With these two settings enabled the drops and be anywhere from a couple of hours to a week apart.  But still, are there other settings to try that will eliminate this problem?

Just FYI:  I have a cable modem and a relatively modern AC router.  I don't have connection issues with other non-dell equipment - more on that in a bit.

The second wifi problem I am having on the E5440 I also have on a 2017 vintage Inspiron 5570 with the Intel 3165 adapter.  That is the problem where the wireless speed will drop from 115Mbps to 30Mbps and get stuck there.  On the E5440 it can get stuck as low as 1 or 2 Mbps.  It is easy to fix.  All I have to do is shut off wireless and then immediately turn it on again.  Then I am right back to 115Mbps on either machine.  What can be done to stop this?

These  problems did not occur when the machines were new(er).  I do not have Smartbyte installed and have not had it installed for years if ever. The router I have is faultless as I can get perfectly good results on a smartphone sitting directly in front of either misbehaving laptop.  Also, I have non-Dell laptops that don't have these issues either.

Any novel ideas would be greatly appreciated..