Instantly is needed to scale outbound.
Hubspot is a CRM with limited outbound capabilities with risk of damaging reputation of your main domain.
So it depends on the scale of outbound.
200 response doesn't necessarily indicate that a domain is valid. A parked domain or domain with empty page would return 200 as well.
I use Claygent with cheapest llm models. In the prompt I also instruct to if content of home page is relevant.