Will be using this mainly for livestreaming. 1080p30 is the max resolution & fps I will be streaming. Will never do a 60 fps stream. Livestreaming mainly through OBS, and once in a while with Wirecast. I've noticed that a 5th gen i5 quad core does quite fine with 1080p30 on OBS, so maybe that can be a baseline for the laptop CPU.
Thunderbolt 2 is the main requirement. I have a Blackmagic Ultrastudio Mini to bring in the video feed through an SDI. The Mini also supports sixteen audio channels over the SDI, which is crucial for me. Unfortunately the Mini comes in Thunderbolt 2.
I've seen a few Windows laptops under $700 with thunderbolt 3. For eg. Lenovo Yoga 730. I was hoping to avoid having to buy a Thunderbolt 3 laptop to avoid having to purchase a converter. The Lenovo for example will need a converter for Thunderbolt 3 to 2 and for the ethernet, which is crucial for livestreaming. That would add another $80 to the budget.