Do enchants, gems and reforging matter for the weapon used by your Felguard via Glyph of Felguard
No, the statistics on the weapon don't matter. The purpose of this glyph is to allow you to customise the aesthetics of your summonable pet by changing the weapon it wields. Many of the weapons that are recommended for the looks at the time this glyph was first added are, in fact, level 60 raid gear from Vanilla.
As the statistics on the weapon don't matter, neither do gems, enchants, or reforging.