Easy part first: A 4070 Super will not launch with 16 GB VRAM. There are not enough memory controllers. The 5000 series is too far away to worry about, and depending on what happens with gddr7 you might find that a 5070 card still has 12gb vram anyway.

TDP only matters if your PSU cannot support the bigger card, or you are using a small case. The electricity savings for a gaming computer are minor.

If your case is not large then a 4080 might not fit. You may need to include the cost of a new case into your value.

12GB of VRAM should be fine at 1440p. There will be a few games where you need to turn some settings down, but it should not be a dealbreaker.

It's really a matter of frames per second. I bought a 4080 to pair with a 170hz 1440p monitor, and it mostly does the job. I still have to turn settings down in some games to get 167 fps. With a 144 hz monitor, perhaps a 4070ti, or a 4070 with a lower framerate or some more settings turned down on newer games. It's your choice.

If you never use raytracing or dlss, AMD have some 6950xt going very cheap.