It depends on what you want to do...

Fist of all, what kind of ammo do you use?

If you want to achieve faster speeds... increase drawlength or cut the bands tapered.
(or both)
If you want to shoot bigger stuff, there is no better way to describe it but with Jörg´s own words..."double up the rubber"

Always try to match the Bandset to your ammo...

 

I am currently shooting 8mm steel balls - however i would like to shoot up to 12mm approx.
I will try the double layered TBG -but would also like to try tubes, but not so sure what to go for - short draw length with good power and durability would be nice.... I have been looking at bit at the Theraband red tube. But there is soon many different options so I get a bit lost as I there is too many different options and preferences.

 

I tried theratubes in various colors and i always found,
that they have a very high draw weight for very little acceleration for the steelball,
even the "lighter" tubes, because they dont stretch as much as bands do.
I would recommend dankung tubes... way easier to draw but
way more flexible and stretchy than theratubes.

But you are right. the market for latex (bands and tubes) have become very confusing.
Maybe there are some test-videos on youtube... otherwise you will have to find out yourself.