4 is entirely possible, J20 flies just fine with 4 2400L drop tanks installed. It doesn't even interfere with the IWB air to air missile carrying, but range might get reduced by quite a bit.
The smaller PL-XX seems to have the same length as PL-15. Its just much thicker. I wonder if J-20 IWB is capable of carrying these. If they have sufficient depth, they should be able to carry atleast 2 internally and possibly 4.
Only PL-15 is correct. The rest is pure speculation, meaningless.
I have doubts about PL-15. On May 7th, PAF killed IAF aircraft using PL-15s that included at least one kill with an extremely long range of ~190 KM. How did they do it when the head-on range is 180 km?
That's how the russian do it, short and fat. So far they are the only ones with operation bay-combatible VLRAAMs. I'm sure at least theoretically the J-36 could fit a fatter PL-17 like missile with 1000km range in it's larger bays. While the other 5th and 6th gen could fit a fatter PL-15 like missile with say 600km or so range, which is still a great increase over current types. Considering that bay compatible VLRAAMs are the next need to have for the major powers, hopefully China is already working on this/testing hardware.
Range is not a static figure. It depends on various factors like initial launch speed and altitudes, not to mention probability of kill on the target is also based on many factors like it's speed, heading, altitude. The farther out you go the lower the probability of kill on any target. It's very likely that PL-15 has a theoretical max range that goes well over the 200km mark. However depending on the target/launch platform the PK may not be optimal.