Your computer specs are exactly what I need to know.
Windows 10 does require more resources than Windows 7, so the same computer will indeed be slower on Windows 10 than Windows 7. But the difference should not be noticeable.
However, if Windows 10 is running on an HDD though, it will be very slow.
The Thinkpad T460 is a computer with a lousy disk, its a hybrid disk and I believe its performance is too low for Windows 10.
I believe replacing this disk with an SSD will improve the problem.