These 3 people have different roles in the delivery of a building. Although there is a lot of overlap they cannot provide the exact same services. Your choice should depend on the services you need or desire.

In order to advise you I would need to know quite a bit more about you, your expectations, your budget, the project conditions, the current design and the experience and capabilities of the people you are considering.

There are rarely simple answers in the design and construction of buildings.

Welcome to the forum. Since you've been reading for a while you've seen the range of opinions, and the tough love.

Renovating an older home, 1800s? How much investigation of the house did the architect do? Hopefully you and the architect know quite a bit about the house at this point and could share with us. I'm not sure how large of a project this is. Presumably there have been a number of alterations over the years to varying and uncertain quality. Possibly materials that would be hazardous if disturbed through demolition. Or was everything completely renovated in the last 30 years?

If there's been some investigation, then you might want to keep your architect. Rather than get someone possibly less qualified to do the construction documents--someone different who will have to play catch up or may not even ask any questions or be aware of all of the existing conditions before putting pen to paper.

If you're not going to get enough details with this architect and you have a very specific outcome in mind, then you might as well write the check to someone who will give you that. But keep in mind that while it's never to early to think about details, you might not see them in the drawings now, depending on where you are in design and the architect's scope of services. Have you seen examples of construction drawings produced by your architect?

Anyway, if you're concerned about total cost, stay with an architect and reduce the number of unknowns before the builders bid. At the end of the project it might be architect ($$), home designer ($$$), design-builder ($$$). Builders bidding on the whole thing right now would be assuming a lot of risk, and would rightfully account for this in their bids. Going with one builder means no competitive bidding.

If the architect doesn't have a good understanding of the existing conditions, then no one should be getting the "thing drawn up" and you might want to consider a different architect.