I went through this about 18 months ago. I tried a BG harness, which is fairly standard design and a BG brace comfort which attaches to your belt or pants at the back. Both work to a reasonable extent but I found the brace easier to use. The standard harness is fine for relieving the strain but with a tenor it puts your thumb in awkward place which soons causes pain in the thumb joint. The clip is too close to your body. I suspect this may not happen without other size horns but did with my tenors. The brace version allows freedom of movement.
I used the brace pretty successfully for about 6 months and during that time I did exercises to increase the strength of my neck and shoulder muscles. I will still use the brace but in the end I got bored with attaching it to my pants and bought one of the newer Cebullas with the wider connector and better padding.
The Jazzlab does what it says and does seem to reduce the weight but I couldn’t get comfortable with the feel, others will recommend it wholeheartedly and if it works for you it is a good choice.
Any of these will help but for my money the best way to go is the brace and some exercise.