I don't have much opinion on the holographic principle as I haven't studied these carefully. This is in fact quite far from what I am working on (high-energy physics is a vast territory). I know some physicists work on this, which is good as we need to be pragmatic and consider any options (as long as these options are not excluded by data).

For the many-world interpretation, this is an alternative way to interpret quantum mechanics. As above, it has not be proven wrong although some see flaws in it. I have personally... no opinion. I feel comfortable with the standard Copenhagen interpretation (that allows to explain data very well). I know of course that other possibilities exist, and that they have at the end of the day pros and cons.

PS: Sorry for not providing any clear answer, but I don't have any here. I know where my personal limits are.