3d carving improvements with linear Z

I’m about to upgrade to the cnc4newbie Z-axis with the high speed screw. I’m curious how this has affected your 3d carving finishing passes? Right now I set my finishing pass at 120ipm, but the Z axis speed is so slow it probably hardly gets past 30 or 40ipm, effectively. I’m curious, with the high speed screw and linear Z, it has to increase speed substantially, right?

The default max rate for the z axis is only about 19 ipm. The fastscrew will reqiure an adjustment for steps/mm. This will notchange your z rate.
You can adjust yout grbl setttings to increase z rate.

Can the standard z move quicker accurately?

There are many factor to your question.
If you are doing 3d carves and do a roughing pass first then I will say yes the stock Z can do a great job at higher rate. Typically with a 3d carve your step-over is very small which creates very little load on the axis.
Many users including me notice chatter when cutting aggressively with standard end mills in the X direction.
Many claim to have eliminated this with an upgrade to the CNC4 Newbies. And I believe that is due to a more rigid assembly without V wheels. That will be my next upgrade/revision.
I personally use a modified stock Z (increased travel range) and have revised my grbl settings to increase max rates 50% and have learned when I can push it and when I cannot.
It all boils down to your process and needs.

so you don’t have a linear z?

No I do not.