The Streamlight Plug-in Remote Switches are not compatible with the TLR-8. These switches will only fit the TLR-1 and TLR-2 weaponlights.
This item is only compatible with Streamlight prodcuts.
You will need a compatible battery door, which can be found here: https://www.opticsplanet.com/streamlight-tlr-battery-door-switch-assembly.html
Recommend reaching out to manufacturer for that information.
Yes, they should be compatible.
They should all be compatible.
There differences between the three options on this page are:
69134: coiled version (designed with pump shotguns in mind) with standard tape switch with mounting clips.
69135: straight version for long guns, with standard tape switch with mounting clips.
69132: straight version for long guns, but designed to fit grips made to hold a switch.
All of these models should be compatible with that grip.
The Streamlight Plug-in Remote swtich replaces the standard battery door/switch on existing TLR-1 and TLR-2 lights, and must be used in conjuntion with Streamlight battery door switches.
The Stark Vertical Forward Grip with Switch Pocket provides for the mounting of a pressure switch for weapon mounted electronic accessories, so it is most likely that yes the Streamlight Plug-in remote switch will fit that forward grip.