A texturizer is of a different chemical makeup and meant for those with shorter hair, although they now make texturizers for longer lengths to relax the natural curl.
Texturizer is pretty much a curl/wave kit to loosen/enhance curls.
Texalaxing is the process of using a relaxer and purposesly underprocessing the hair. So leaving it on for a few minutes or so to loosen texture.
So they are almost the same thing but different. You can't apply a texturizer kit and then try to change over to a relaxer(to texalax); you can but you can't overlap the two as it will cause major breakage.
You can achieve the same look with either just be mindful of which chemical kit you want to use.