xenia cant sting. it can grow over other corals, and shade the coral to the point where the zooxanthella dies and starves the coral to death.
IME, sps are the weakest. they loose the battle to lps and soft corals, like 95% of the time. LPS are probably the strongest, because of there sweeper tentacles, given the chance though, soft corals can take over lps.
IME, soft corasl can tuch without any problems besides growth issues. ive had, xenia touching shrroms, touching zoas, touching leathers. the only problem was that occasionally, another coral would out grow/ grow over another. this is most common in GSP.
but to go against what i said above, i currently have a purple rim monti capricornis outgrowing GSP. ive never seen this before, but the two merged, and now the cap is growing over the gsp, causing the gsp to retreat.im gunna try and get some pictures soon.