A given project should only be restricted to 9.5 if that projects opts into whitespace and invisible character support. Once that happens, that specific project can never* be opened with a previous version of Paratext again.
Just using 9.5 on your machine should not change any projects to require 9.5.
* It could theoretically be undone, but the process could only be done with support staff leading you through a fairly complicated procedure.
