IMO, type 071, 075 and 076 each play a not so slightly different roles in an amphibious assault.
Type 071 has 4 LCAC, a hangar for 2 Z8 helicopter (plus 2 more on landing deck if needed). The 4 LCAC would be key asset to deliver non-amphibious tanks like type 96 and type 15. The ship can also launch several dozen amphibious tanks and IFVs. Thus type 071 is designed with bias favouring on delivery of armoured vehicles rather than foot soldiers and mountain cat type of vehicles.
I don't know how many LCAC can be fitted inside type 075, but it is obvious that it would mainly be used to airlift foot soldiers and light vehicles for speedy landings. It's LCAC can carry MBTs just as type 071 do, but airlift would be its main strength, especially if assault landing zone would be located far inland.
We still have very limited knowledge on Type 076. The obvious feature that we have seen is its catapult. It would carry a lot of helicopters and a lot of drones. There is a wide range of uses for drones and helicopters for offensive, defensive, medical evac, recon etc, and due to its displacement size, it's capability to deliver assault forces onto the beach would not be less than type 071 and type 075.
How they would be deployed individually or in combination depends on the mission and scale of the assault operation.