There are some elements of answer already available, but nothing regarding the sliding-scale calendar.
Macau has imposed a daily 50-return-trip limit for coaches, one round-trip per coach. Sixteen licences have been issued to Macau bus companies, and 34 to two HK consortiums. So there will be 50 buses going daily to Macau and back. About two an hour, average, although I guess the schedule will not be a flat 30-minute departure schedule all day. The buses are supposed to leave from Kwun Tong, eastern HK, stop a couple of times on the way, and then cross to Macau, stopping at casinos. Considering HK's traffic, these buses are going to take forever, at least during the day.
Then, people will have to get off the bus at the immigration facilities near the airport, pass through immigration, and board the bus again. There is such a scheme in place at the HK<>Shenzhen border crossings, and it isn't pretty. Add about 30 to 60 minutes to that schedule. It will take just ONE tourist on board to delay things.
According to Macau's government stats, in the first quarter of 2018, 2.6 million peole arrived in Macau by sea. Including a little under a million PRC people (which gives us a good idea of the HK<>Macau sea traffic, since arrivals by sea are either from China or HK). Assuming 1.66 million people coming from HK, over 90 days, that's about 18,000 people PER DAY. A bus can carry about 60 people. Fifty of them will carry at best 3,000. Assuming full capacity on every single bus. That's about 15% of the traffic, optimistically. As a comparison point, during the same period, there were a total of 8.5 million arrivals, all included, 6 million of which Mainland Chinese. The border crossing in Zhuhai is busy indeed.
The two operators for HK are OneBus and Kwoon Chung. Kwoon Chung's existing website sucks balls bilingually (they're a very, ahhhh, traditional company) and I don't expect them to provide much in terms of information, when they start. I'll keep digging in the coming weeks, until they and OneBus publish something.
I'm interested in trying it once. But I'll probably buy not even a round-trip, just a one-way ticket.