Is using a snell knot limited to only straight shanked hooks?

Can I use it on a t-rigged off-set worm hook or an off-set ewg and it still be an advantage?

Yep, I use it with any hook when using heavy tungsten weights so the weight won't damage the knot.

If you don't want to mess with a snell, I just use a bobber stop above my knot.  I punch with 1.5oz tungstens and have had no issue since I started using the stop.  It's easier than tying a snell knot on an EWG offset for me.

Just do all your work on the straight part of the hook but leave it loose then slide it around the offset and pull it down tight. Pretty easy to do..

Tying is no problem, just wanted to make sure the way it kicks the hook out wouldn't create hook-up issues with other style/shaped hooks. Thanks

I was watching Big Bass Battle (whatever the Lake Fork sponsored show is called) and the host was using a snelled offset EWG hook. 

I was watching Big Bass Battle (whatever the Lake Fork sponsored show is called) and the host was using a snelled offset EWG hook.

Yeah I saw that to. I gave EWG's another try the other day and used a snell knot.....still a terrible disaster. Every hook-set pulled straight out of their mouth. Swapped the EWG out for an off-set worm or straight shank and start hookin up immediately.