Well, at least we're all agreed about anything called "mire" - avoid!
FOX160 you make the point you have never walked on the moor and it's wise to bear all that means in mind when planning. The suggestions made here are pretty good but you'll need to discover if (and how) what you can do is what you'd like to do, and that'll begin on your first trip. Anyone can make suggestions but what you do really will depend on you. It's an ability that should improve with practice. Where you can bike may be a lot different from where you walk BTW.
I note your interests and the websites I mentioned have photos that may show something of particular appeal to you and give some useful idea of surrounding terrain.
Dartmoor isn't noted for drying out in a hurry, but more the opposite. Some parts are always wet. Always.The weather there doesn't let up but is constantly present in some form as you'll surely notice, some of it being more welcome than others! It's an exposed upland area in large part and the general advice to be prepared for quick changes in weather is foolish to ignore at any time of year, some more so than others. I tend to agree with the adage that there's no such thing as bad weather (it's simply weather being weather), but it can become obvious that there is gear ineffective to deal with it. Those of us who find effective kit tend to regard and care for it with affection for the welcome comfort it brings! The rest tends to be cursed. All part of the moorland experience I think.
The varying weather conditions are often what adds to the magic of being on the moor. For some reason I have a particular liking for fog, finding it to bring an excitement and challenge that is relished. It's not for everyone, especially the less confident or uncertain types. Hot, cloudless, still days I'm not so keen on, preferring the cool effect of a breeze when hiking on a warm day and the interest or shade from a cloud or two. Each to their own eh?