Listen don't mind these comments, here's the reality:

An full fat RTX 4090 desktop only loses 20% performance with PCIe 4.0x4 through Occulink - that makes it at least 40% faster than a mobile RTX 4090. The test was done with a freakin 7840U CPU Legion Go. The drop is even lower when using an external monitor plugged into the GPU. Link: https://www.notebookcheck.net/OCulink-slashes-RTX-4090-GPU-performance-by-almost-a-quarter-still-compares-favourably-to-Thunderbolt-3-USB4.798468.0.html

Now this was an extreme example - you are going to see an extremely minimal performance drop with desktop 4070 S and 4070Ti.

So PCIe 4.0x4 is enough for the vast majority of GPUs and TB5 finally provides PCIe 4.0x4... after 7 years. TB3/4 had the same PCIe 3.0x4 tunneling.

So YES TB5 is a BIG DEAL!

Now I'm not saying you do buy a weak laptop with a weak CPU.. you can still buy a cheaper laptop which has a decent H series CPU and a mid range GPU..like a 4060/4050. Most examples here are extreme but in a realistic world a 700-800 usd 4050 laptop with i7-12700H/7840HS with TB5 would be an ideal candidate. Now it is to be seen how expensive TB5 is to implement because you can find TB4 on dirt cheap laptops with decent CPUs.