Are ray tracing and multi-frame generation worth paying more for at 1440p?

At double the price, I'd take the 9070 XT. The 5070 Ti has advantages in ray tracing and DLSS upscaling, but it doesn't deliver anything close to double the performance. A smaller premium would be a different conversation.

The AMD card can run ray tracing too. Check benchmarks for the specific games you want to play, with the settings and resolution you actually plan to use.

Ray tracing can make a real difference to lighting and reflections, so I wouldn't dismiss it as a gimmick. Whether it looks good enough to justify the performance hit varies a lot by game.

The bigger NVIDIA advantage tends to show up with path tracing, which is especially demanding. Even on the 5070 Ti, you may need to make compromises on resolution or performance. If that's the feature you're most excited about, look up comparisons for those particular games before deciding what it's worth to you.

I'd treat multi-frame generation as a bonus, not the reason to buy a card. It can make motion look smoother on a high-refresh monitor when the underlying frame rate is already good, especially in slower single-player games.

Generated frames don't make the game respond as if it were rendering all those frames normally. Latency and visual artifacts can be distracting, and some people dislike the image quality at higher generation settings. For competitive games, responsiveness may matter more than the displayed frame rate.

Since you're shopping used, compare the condition and seller terms as well as the model and price. A cheaper card is less appealing if you can't verify that it works or have no recourse if it arrives faulty.

For the monitor, check variable refresh support with whichever GPU you choose. That matters regardless of whether you use frame generation.