Lots of
Good Info here.
Grab Bars: I havn't done any searching yet on Shower Grab Bars yet because ..Frankly I hadn't considered myself to be in THAT "Catagory".....
YET. I suspect that Grab Bars are NOT JUST screwed into the wall.
What is
Behind the wall (Facade) will be important. My house was built in 1973. Was it Sheet Rock behind the ceramic tiles..OR was it Greenwall..? (If that is the correct term). I would think
..."Through Bolting"....to something
Substantial behind the tiles and Dry/Greenwall would be required.

NB
EDIT: My engineering background quite often gets in the way of "Consensus".