Diablo – Plus signs in Diablo 3 for ps4

Monsters spawn in zones. Zones determine the levels and kinds of monsters. This is the same regardless of the number of players.

Scenario one: Solo level 15 in a level 15 zone. Fights enemies and gets some amount of xp per kill (suppose it's 20 xp).

Scenario two: Two level 15s in a level 15 zone. Fights enemies. Each player gets the same xp per kill as the soloer in scenario one (each player gets 20 xp for each dying monster). Adding a player increases monster hitpoints and quantity spawned.

What about level differences?

Well that's answered over here: How does experience work in groups of heroes with different levels? The only difference on console is that you are never out-of-range to earn xp. So xp is always copied perfectly between characters playing together (except with death, untested).

Will it be playable for both types of players?

No. Level 15 monsters will destroy level 1 characters. Level 1 monsters will not reward level 15 characters.

The quality of the items (power) remains the same. Just the drop rate of rarer items is increased if you increase the difficulty. The power (item level) depends upon your character level. Same as in PC-version, by the way.