Your Tac-14 already has a Magpul forend on it (I had to add one to my Shockwave). I just installed a short piece of M-Lok rail and then added an InForce WML. The button is right where my thumb can access it easily and it provides great illumination. Any sort of vertical or angled fore grip will just be for mall ninja effect, although some Talon Grips decals will give a stickier, more sure grip. If you're worried about getting your hand out in front of that short barrel, a Magpul handstop can be added to keep your fingers away from the muzzle and safely attached to your hand.
BTW, you'll want to be careful about adding a folding brace to your Tac-14. The original bird's head grip puts it at just over the legal length (26.3") to fall into that magical gray area of being a "firearm" and not a SBS under the NFA. If the gun fails to measure greater than 26 inches in length with the brace folded, you might be putting yourself in legal jeopardy. I added a pistol brace to my Shockwave, but eschewed the folding option for that exact reason.