Payload, speed range do correspond to each other.
You cannot expect a max. payload with max. speed.
The MAX. payload for the He-177A5 is 7200 Kg of bombs inside the bomb chamber.
Usual configuration was somehwat lower:
either
A) 48 X 70 Kg bombs (3360 Kg / 7405 lbs total)
or
B) 10 X 500 kg bombs (5000 Kg / 11020 lbs total)
or
C) 6 X 1000 Kg bombs (6000 Kg / 13224 lbs total)
or
D) 2 X 2500 Kg bombs (5000 Kg / 11020 lbs total)
or
E) 1 X 7200 Kg bomb (?) (some planes only, 15869 lbs total)
or
(Note that A)-D) is also true for the He-177A3)
If the bomb chamber was empty, the He-177A5/U could also carry under the wings:
2 Hs 293 + 1 Hs293 remotely controlled missiles under the fuselage
or
2 Hs 294 + 1 Hs 294 remotely controlled glide bombs under the fuselage
or
2 PC 1400 + 1 PC 1400 gliding bomb under the fuselage
or
2 torpedoes + 2 torpedoes under the fuselage
As You see, the average payload of the He-177A5 levelled somewhere between 3t. and 6t., depending on mission requirements.
Now to Max. performances, such as service ceiling (WITHOUT PAYLOAD, the -A5 had 7000m service ceiling at max. payload achieved during missions) and max.speed and range(again without payload):
He-177A3 with two DB 606: 9000m----480 Km/h---------3700 Km-------(298 mph for 2300 ml.)
He-177A5 with two DB 610: 8800m----440 Km/h---------3650 Km-------(273 mph for 2267 ml.)
He-177A7 with two DB610A/B: 9400m--540 Km/h--------3700 Km-------(335 mph for 2300 ml.)
The He-177A3 was the first serial variant to be delivered in larger numbers to LuftwaffeBomber Gruppen. The very first 15 planes still had DB 606A/B with 2700 hp, which were very sensitive to cooling issues, later units had 2900 hp powerplants.
The He-177A5 was the major production model with a somewhat underpowered DB 610, which in turn seemed to be less prone to inflame (it still remained an issue).
The He-177A7 had furtherly improved powerplants and a larger wing area, which should help to improve range and speed figures altough only few A7 left assembling halls.
These datas come from original Luftwaffe docs analysed by:
H.J. Nowarra, Dokumente der Deutschen Luftrüstung 1933-1945, Vol. 2, 3rd edition (Koblenz 1993).