I think it depends on the individual dog.
Two of the best 'lurchers' as opposed to Longdogs, that I've seen over the years, was my ex brother in law's whippet/greyhound x bedlington, 20.5" tts and 31 lbs in weight, used to catch a good number of hares on all types of ground, and would, as you say, practically float over heavy/boggy ground.
Not real coursing, but mooching daytime, lamping etc.
And my old dog, sired by Hancock's Taffy and out of an exceptionally fast greyhoundy mongrel lurcher.
My dog was 26" tts and just about 80lbs. Again, not coursing, as such, but daytim