Can I replace a laptop with and ITX or Matx or Mini Pc perhaps

I am considering building a system that I’d like to be able to use with some ML stuff down the road. I’d love to build a Threadripper or Epic. The quNdry I have today is my laptop mobo is rekt and I need a system. I’m looking for suggestions regard for a factor choice. In my mind I’ve come to believe an ITX or Matx system in the right case with the right portable accessories would work for my limited travel and would outperform any laptop. Now I’m curious if there’s an economical way to get it to a Threadripper system or epic Machine Learning Rig if I forget about Porta ility and just buy a cheap. Laptop for that. What’s the entry level into that world that I can build on. Tha KS