I'd say go whatever you think looks cool but make certain you use the same bits throughout your army. One thing I would advise you to buy is guitar-string, it's great in making noise weapons out of regular bolters and such.
Just use a regular bolter, add guitar-string for pipes/lines etc. (put one end into the weapon and the other end in the backpack or under the shoulder pad), replace the muzzle with vox-pieces or some such. I have even seen old possessed marines' heads used as "muzzles" which looked great
IMO. Also, cut off the magazine as it's not necessary. It looks a bit silly if the magazine is still on it.
I don't know what you have in your bit-box or how many noise weapons you'd need but I can tell you that the official weapons are a pain to put together and you are probably better off converting anyway. I used all official bits for my Noise Marines and it drove me nuts as it takes a lot of pinning.
The examples you put up look cool