Let's see if I can help you out a bit. I found some culture information for Den secundum, Den smilliae and related species here:
How We Grow Dendrobiums, Part 4 – RF Orchids
They do well potted, mounted or in baskets, with people opting to mount due to their size. So how you pot your Lee Chang Yi Miriam will be a matter of preference, how much experience you have with mounts, and how suitable your environment is for mounts. There is temperature and light guidance in the article, which should be useful to you. Basically it needs to be grown warm/hot and in bright but filtered light conditions. You might struggle a bit to keep this one happy in the winter, temperature wise.
As to Den amethystoglossum, it seems like it will like rather different temperature: not too warm and good in cool weather in the winter. Light should be diffused, so your porch sounds like a good place for it.
At the very end of this thread is the Bakers' culture sheet from Orchidwiz:
Dendrobium amethystoglossum
I hope this helps you a bit, though it would be nice if some people with first hand experience with these could give advice! Though it seems that not many people grow these, there's not much mention of them in the forums and questions about them go frequently unanswered