Hi,
I use Boss NS2 that way with Helix. Path: Guitar to NS2 input -> NS2 send to Helix Guitar input -> Helix blocks synth, Fuzz etc. -> Helix loop block (send to NS2 return, NS2 output to loop return).
I use this with Helix 3 Osc synth to get rid of unwanted tail sounds. Downside of this is that it takes two loops from Helix.