I think there are only two professional brokers in the wild right now, one is sick and the other is out cruising. The rest just call themselves brokers.
I sense there might be subtle differences by region. Ultimately, you must have a contract and 10% deposit. That seems a constant. Whether an offer will be communicated verbally, might depend on circumstance.
I guess, if no party really knows you or you appear to be a tire kicker, the process can get more formal. If it's a broker you've used before, as I have, they are the one that is going to hold the money anyway. The seller never sees it until closing. In fact, never sees it at all, since it is the same as the brokers commission. Its sort of silly to have an uncashed check sitting on the desk of a buy side broker the seller has never met.
Regardless of formality, they always present the offer verbally, even if they have it in writing and check in hand. They want to communicate what the paper never does. This is a good buyer. Your boat may not sell for another decade. Etc. They do want to get a deal done to be paid.
There is an irony to proferring in writing. While the seller may not accept a verbal offer, the buyer really doesn't have a committed seller until they receive the contract signed by the seller.
The contract ties the seller hands more than the buyers.