Personally I only use an Ice bong as ROA, Sweetpuffs just cannot provide me with the rush, but I've never IV'd. Fortunately I have the capability & equipment to produce my own bongs & glassware.
To answer your question,
I would say the main differences between the 2 set ups you have tried is the size of the "venturies", or if you like all the passages that the air/vapourized gear travels through, from the hole where you put the gear in the bowl, until it reaches your lips.
Some of the cheap Asian imported rigs I've seen and used over here have very small passageways, which is a restriction on air flow. And as I said I don't know what set ups you've been using, but the size of the holes/passages definitely matters.
This is basically how make mine.
Over here in Australia, Red Bull comes in a 330ml aluminium bottle, that will become the chamber.
I used to Dremel holes in glass bottles to put the stem through, this is much simpler.
Then I will blow an extra long stemmed sweetpuff out of 10x2mm boro glass that has 3 or 4 bends in the stem so it fits through the hole & into the chamber, and reaches to the bottom. Punch a step drill through the can at the bottom of the neck, add a rubber through grommet, insert glassware, done.
The hole size where your drop the gear into the bowl, in all my "research" needs to be decent sized, like 3/8 - 7/16 inch, this increases air flow to give a much more desirable user experience....
I must also add,
I do not promote the use of Meth.
I am no way encouraging the use whether recreational or otherwise of this substance.
I can & will destroy lives of otherwise intelligent beings that have far greater potential.
I was young once, never listened.
Everyone has their own lesson to learn.
Please,
Be safe,
Take care of yourself.
Peace
