I have question about CtA

is worth it 2x CtA PB for barbarians or what do you reccommend for mf barb weapons

You'll get max +3 BO bonus and this only one time, so 2 CTA on Barb is +5 BO. If you want to maximize BO 1 CTA 3+ BO and 1 magical echoing weapon gives +7 BO and is the best afaik.

My MF Horker got 2 6xIst PB on switch but having Echoing PB with 2 Larzuk Sockets filled with Ists is also an option i've seen.

For main weapons, Grief is far superior damagewise

There are actually quite a few arrangements of Barbarian weapons for you to choose from, depending what you're running and what you want.

As mentioned by Blubb, items that give +oSkills, or other class skills, do not benefit their native class very much. Hence why Trang-Oul's set isn't BIS for a Fireball sorceress. As such, CTA is an awful idea for a barb in all scenarios.

In terms of MF weapons, the first question is your build.

If you're using Enigma, such as a Pitzerker build, then your best weapon set is likely Grief + 6os Phase Blade filled with Ist runes main hand. This gives you a ton of MF and allows you to use FCR items on your swap.

If you're not using Enigma, you can still run Berserk with the 6os + Ist thing from above. In that case, on swap you could have Echoing spears for +6 to BO.

If you aren't running Berserk, or don't want to do the 6os + Ist thing, then you can use 2 damage weapons (Grief, etc) on your main hand and MF items on your swap. I like gambling, so I personally use 2 Blade Of Ali Baba socketed with Ist runes on my WW barb's swap, with my main hand being Grief + Oath/BOTD. Using 2 6os + Ist phase blades on swap also works here. Gull can be a cheaper variant of this.