When u are using Physics for clothes… its best practice to not use metahuman clothes… when making the metahuman… u want to not take any clothes built in the metahuman creator cause the parts hidden behind the clothes of the character wont be rendered therefore the metahuman would not have those parts… just dont select any clothing… and probably make something in software like marvelous designer or cloth3d…
As for the head not being attached to the body… there are videos on how to join the neck and body of a metahuman
If u are concerned about having to run the animation on all skeletal bodies of the metahuman(if u have clothes)… that is not the case… if u open the folder created by metahuman in your project… there should be a blueprint of ur metahuman… (u can also just search “BP_(name of ur metahuman in the creator)”)… the other parts of the body would be setup to be children of a “body” skeletal mesh… to play animations u just have to play it on the body mesh… to migrate it u need to copy all the blueprint code to ur made character blueprint…
Hope this fixes all your issues…