ALSO Choose Remember each folder's view settings THEN Close Explorer to memorise the settings. THEN Relaunch it to check the results. You may find the window dimensions have changed, and if required you can now drag them again to what they should be and exit again. This time both the column layour and the window dimensions should be remembered.
Optionally, you can then unselect Remember each folder's view settings, so that in future it will always come up as first remembered.
ISTR, there is also a relevant Group Policy Setting, but can't seem to find it ATM.
Eh?