For example, can i use the SLITio extension by symzy to zoom out?

I think it is allowed because there aren't any rules against it, but there probably should be. Either that or have 2 sections: Non Extension / Extensions with the 3 sub categories within them.

Thanks for the Posts, I have decided to make Extensions against the rules. This is because some players may not be able to access them for their runs. Updated the rules to accommodate for this ;)