Cool that you like it! :)
I don't know where to find the samplers in the source code, but I bet the InvokeAI team can help you on their discord. :) Also, they are working on the big 3.0 update that will allow plugins/nodes, so adding a new sampler should be pretty easy by then. :)
And for AI the 3060 is usually better than the 3070. :) The 3060 has 12 GB of VRAM (compared to the 8 GB of the 3070), which allows for *much* bigger images than the 3070 would. :)