I'll try to help a little, although I never have owned the Defy 7 (heard a few marks of it often, particularly the original).
1 and 2. The earliest versions of these amps were fairly "ripe" in the bass--i.e., they had lots of mid bass, and sound like they're putting out a lot of bass, but the deepest bass was overblown and fat, the opposite of tight bass. The later marks of the Defy may have improved the Defy in that area, but I don't know if you really can get "tight" bass from any Jadis products; my impression was that the later marks really were more like better refined versions of the original. For example, my Jadis JA80s are a far better amp than the original Defy in terms of refinement, but the Defy has more raw power. The later marks of the Defy started to approach, but never equalled in my view, the 80's refinement and subtle detail. I don't think you can categorize any Jadis amp as having bright highs; most are rolled off in that area, although the Defys using 6550 tubes might have a little glare in the 1-2khz area compared to those using KT88s or KT90s (the original version of the Defy could only use 6550s, which have decent bass response but are not as good in the midrange, in my view, as other tube types; I think later marks could be adapted for other tubes, but I'm not sure of this).
3. The Defy should have no trouble driving a speaker with the sensitivity and resistive load you mention; my JA80s easily drove Duntech Princesses, which are the same load you asked about, and the Defy has more grunt than my 80s.
4. As far as noise goes, don't expect it to be dead quiet like solid state, that won't happen. Tubes will always have some noise (and the Defy uses a lot of them), and older caps and resistors in some used units may intermittently make some spitting noises; I learned to listen through those noises, but they will be there and dependent on the condition of the amp and of the tubes in the unit.
Hopefully some owners of the Defys will speak up, but these were my impressions.