Alpha king titan is a world boss, bring as many as you want. as for the others, i dont think you can bring bosses to boss arenas. To check what is a boss or not try to put it in a cryopod.

If anything is over 550 drag weight they cant enter the boss arenas

With the exception being moeder i think you can bring kaiju like akuky ry to it though idk why youd want to

If you want to bring them to arenas you can use the all arena+ mod