>>>Does it resonate or impart a sonic signature to the TT?
EVERY device will impart some of it's own self generated signature but the VW is fairly benign with the stock Target particleboard shelving.The glass shelf version has a fairly strong and persistant sonic character.
>>>How much weight can it support?<<<
It's rated at approx 45-50 pounds but ime,the main determiner is how secure it is mounted to the wall. Fastened to an exterior load bearing wall and tied to the studs securely,I've had decent results with equipment weighing in at up to around 65 pounds provided the weight isn't concentrated near the front of the support.
>>>Would it help, or be worthwhile, to fill it with sand or lead.<<<
No.If you're concerned with chamber resonances,then try tightly stuffing several of the tubes with polyester batting.Just adding sand or lead will be more detriment than help.
>>>What about using the Cloud 11 &/or the Neuance table with it - help or hinderance?<<<
Replacement of the stock shelving of the Target and other supports that feature decoupled shelving with Neuance will substantially improve performance and reduce colourations.The Target VW's are an ideal Neuance application.