How to design a heat bed / radiator using resistors?
You ask: "Are cheap Chinese power resistors like this reliable at 110 degrees?"  Usually, yes.  Dale was the first company whom I saw make that style of resistor and their data sheet says that their parts are good for a maximum of 250C.  Hopefully, your Chinese supplier uses similar construction to the Dale parts.

As always, the data sheet holds the answer.  Since you don't have a data sheet, the best you can do is take your chances.