I went from an AMD 3600 6 core and Radeon RX6750XT to 5800X3D and RTX 4090. I see a significant use of VRAM well past the 8GB of your 3070ti. My 6750XT has 12GB and I used easily 10GB and the 4090 with 24GB still uses only 10-11GB VRAM with TLOD 200 World Scall 100% TAA etc lots of ultra 16X 8X8 etc. My CPU jump from 3600 6core to 5800X3D sees frametime drop below that magical 11.7ms very consistently. This is a huge improvement from the AMD 3600 CPU. The Combination of a CPU feeding the GPU and having enough VRAM to “buffer” the frames smoothly makes all the difference. Regardless of settings in MSFS, 6700K + 3070ti will work but you have to find a way to set MSFS to reduce your frametimes on the CPU and then maximize your GPU utilization. For a smooth experience Frametime is key. I would think upgrading a 6th Gen CPU to current whether AMD or Intel will allow you to feed steady frames to your 3070ti. The 3070ti will still be a problem on HP Reverb G2 due to a near 4K image that is limited by 8GB of VRAM. Devs are really struggling to get this level of realism inside 8GB of VRAM. With my 5800X3D and 4090 I pretty much fly everywhere at 45FPS+ with GPU headroom and 11ms frametimes from the CPU in TAA 100% world Scale and TLOD 200 OLOD 200, except NYC, London etc at 30+ FPS in VR.
TL;DR Upgrade the 6700 CPU first!