Flat = T40RP
Fun = T50RP
Bassy = T20RP
Be aware that you can turn a T20RP into a T50RP by adding some cup vent damping and vice-versa, but you cannot turn a T40RP into anything else unless you remove the piece of plastic that is heat-fused to the cup vents, which can turn out ugly if you're not careful / experienced.
T50RP leaks very little unless you listen to music very loudly, T40RP less so, T20RP more so.
@Romko Levytskyi
I don't own the T50RP and T40RPM, so I'd trust @c61746961 first, but I just want to second his characterizations on the T50RP and T20RP, both of which I do own, both with respect to sound signature and leakage characteristics.
I actually use the T50RP MK3 at work precisely because they leak significantly less than my Senn HD 600 or Grado cans, and I have an office mate that I don't wish to disturb; I only use the more open, leakier 'phones when he's out.