RAE Bedford conducted extensive noise trials 1975-85 which showed significant benefits with increasing approach angle. IIRC the BAe146/Avro RJ AFM has a table of angle vs noise for the full landing config.
One aspect of noise was the aircraft configuration. Engine noise reduction was generally understood, but the effect of the airframe less so; this was studied with overflight tests and a few Tristar ‘under-flights’ below a large noise monitor suspended from a helicopter.
Bedford also studied wake vortex, but I don’t recall any specific trials with steep approach, or any concerns that any change of approach path would significantly affect the wake.
I recall a study of the LHR 27R ‘famed’ vortex from a hangar (bakery?) with a SW wind which affected aircraft on short finals.
There were also operational studies at LHR with split operations where ‘STOL’ (steep approach) capable aircraft would land long, >3,500ft from a steep approach (4.5 deg), with heavy traffic on a normal, or slightly elevated approach. The different approach paths provided wake separation such that normal runway capacity limit spacing could be used for all types. Guidance was with ILS/MLS and PAPI.
These studies were revisited with the advent of the BAe146 at LCY, but not pursued as only a few aircraft were then STOL capable and even fewer operated at LHR. The situation and balance of traffic may now have changed enough to reconsider.
There should little or no concerns about aircraft operation or wake vortex from the LHR trials providing there is no need to change from the normal landing configuration; the noise benefits from 3.2 deg would be most noticeable at distant locations.