I need a new one..are they all born equal?

No.
The cheapest are galvanised steel, then better quality are stainless steel, of which Shimano ones are best in my experience, then there are the PTFE coated stainless ones which work best of all. Some of the cheaper stainless ones are quite soft and kink much more readily than the better quality ones.
Of equal importance is the quality of the outer, Again, the higher quality ones are pre-lubed such as Shimano SP41

Best cabling is still a full length SP41 with a 1.1mm inner (thinner than standard). No point spending “20 or so on gore etc.

I’ve a jagwire outer & X7 shifter, are there any compatibility issues with the shimano cable?

Sram pit stop inner cable is 1.1 as recomeneded for gripshift
It’s not coated but seems to last a lot long than the xtr ones which are great till the ptfe wears off

Casing always sp41 or nokon