Well, it depends.
Octane Render can benefit GREATLY from a better GPU.
Cinema 4D will benefit a lot from the GPU as well for preview, but for rendering, you are looking at high core count CPUs.
The problem with making a Build for AE and C4D at the same time is that they dont benefit from the same thing.
For AE you need high clock speed, for C4D you need high core count.
But, back to your question. I have a RTX 2080 ti 11gb myself and i have NEVER EVER seen my gpu usage go above 20% because of premiere or ae (I only work with fullhd and 4k footage). They are using the CPU all the time. So, the RTX 2070 will be more than enough. But again, not always.
If you are working on 6, 8k RAW footage, a higher VRAM GPU will be of great help.
So, If you go on the 2070 route, try getting at least a 8GB card.
I too work with C4D and AE on the same build. The route I choose to go with was a 9900k and a RTX 2080 ti 11GB. Works ok for me. AE is still slow AF, but thats a software fault, not a hardware.
And going higher on core count would make it even slower, and thats why I invested in a good GPU, to help a little with C4D. And since I use Octane Render A LOT, the gpu helps a ton.
Thats my opinion and my personal experience. I am no engineer nor a computer scientist. I’m just telling you my experience from real world experiments.
You can try emailing puget and reading their articles, they are amazing. And they know a whole lot more than Ill ever do.
Hope Ive helped.