That was very interesting, and just the case you are interested in this information:
My CPU is much more up to date than my GPU.
For your first link (containig 4 rows of flags) my CPU, GPU and power usage (according to the task manager) in Firfox was:
- in an akitve TAB about 1.9% CPU (1.8 to 2.0) and 13.6% GPU (13.4 to 13.8) and power consumption medium to high
- in an inactive TAB 0.1% CPU (0.0 to 0.2) and 0.2% GPU (0.0 to 0.4) and power consumption very low
when hardware acceleration was enabled.

And:
- in an akitve TAB about 1% CPU (0.9 to 1.1) and 0% GPU and power consumption low to medium
- in aninactive TAB 0% CPU (rarely at 0.1%) and 0% GPU and power consumption very low
when hardware acceleration was disabled.
In both cases (hardware acceleration on or off) the animation was absolutely smooth.