FSILEO,
The reality of the situation is that some Engines and Rolling stock will and some will not. The best way to see if a particular 036 rated Engine will run on your 031 or 027 Track is to actually try it yourself, on the particular track you are using, and see what that particular engine actually does.
Still the best thing to due with any Engine & it's rolling stock is run it on the mfg's listed min Track curvature.
PCRR/Dave