1. Currently I am using 3 total: claude on my working laptop and opencode+agy for my personal stuff. e.g., opencode and agy give access to different models, nice to try them.
2. This is what I did actually, but I still did the setup for each tool separately. E.g., if I find a new skill - install that into each tool. Or if I want to adapt system prompt, or something else. Basically things that I would configure for each one. So at least for myself I just have one place to store everything like skills setup, configuration, allowed tools and then it just "renders" it into different configuration format per tool. Sharing dotfiles helps you sync them between devices, but not via different tools. At least I did not find a way