Or, since there is this alternative in Ontario, a licensed architectural technologist.

Homebuilding in Toronto is a highly bureaucratized and lengthy procedure, much different from most of the US.

No matter where you are, building a custom home is not a DIY job unless you are a licensed architect.

You need an architect and they will help you through the process . It is hard to tell from your question but are you already in the building phase ? Waht kinds of must haves are you asking about?

Years ago a neighbour asked another builder and myself for rough quotes. We were both about the same, they said.

But the husband and wife teachers decided they could diy. And they did. I used to count the obvious errors and unnecessary costs.

Finally, in a moment of unasked for revelation when they were done, the husband confessed that they couldn't believe what builders have to deal with. They were both grey with exhaustion (Sorta the way I feel many days!)

Plant the money tree now. And water it well.

^^^^^^

The realtor's presentation doesn't make the distinction between actual building costs and what a builder will charge the client. For instance, I'm projecting hard and soft costs up to C$400 sf on our current build. But if this were built for a client, the builder would expect to net at least $200K-$250K++ in built-in profit.

The diy who figures they're "saving" that profit underestimates building difficulties while forgetting the income they're foregoing in their own occupation. "Hey, justa bunch of blue collar dummies. I can do that standing on one leg with one eye closed."

must haves to get done while framing:

All incomplete decisions.

Prior to framing, all fixtures, cabinet brand, windows ordered, roof material selected, fireplace ordered, HVAC system ready to order,

In Ontario, at the minimum, check that your builder is registered with the mandatory Home Construction Regulatory Authority (Link), which also mandates TARION warranty enrolment.

But if you want to act as your own builder/contractor for your own use, you're free to do so.