Should I stick with the MacBook Pro for heavy video editing?

Regarding the MacBook Pro: Yes, get the Pro. The MacBook Air lacks a fan, so it thermal throttles under sustained heavy loads like 4K ProRes editing, causing performance drops. The Pro has active cooling, finishes exports in half the time, offers up to 128GB RAM (vs 24GB), and more GPU cores. The Air can handle light work, but for heavy editing, the Pro is the right choice.