Assuming the Framework laptop can support Thunderbolt 4, then one port must provide at least 32 Gbit/s of bandwidth for PCIe (equivalent to 4 PCIe Gen 3 lanes). Bandwidth usage depends on the type of load; gaming on a 1060 shouldn’t max out the Thunderbolt 4 PCIe bandwidth. You could probably find some I/O heavy task that would max it out, though.
Unfortunately, you should still expect a performance loss. Running the GPU outside of the computer adds latency, as does waiting for the GPU to write back to the internal display buffer (which is why plugging your eGPU into an external monitor can improve performance). That latency is the real bottleneck. Around 25% performance loss is common, but I believe it’s worse for more powerful GPUs.
It is possible to overcome the latency issues. The Alienware Graphics Amplifier (the discontinued eGPU for some Alienware laptops) had a pretty small performance hit, but that used a proprietary port and some other custom internals. Now, even that only had PCIe 3.0 x4.
Mobile processors typically have few PCIe lanes, which makes it hard to just slap a x16 port on everything. Another user mentioned that the Tiger Lake CPUs only have 20 PCIe lanes.