2m+ travel lengths with a ballscrew, using linear rail to support the ballnut

[JAZZCNC]

If I use 2m+ long ballscrew with 15mm Hiwin's 2 carriages supporting the ballnut will I be able to spin the screw faster without whipping? Rotating ballnut seems unfeasable and expensive so need a way to get speed and accuracy am toying R&P but would be better if I could use a ballscrew of course.

You haven't stated size of ballscrew so not easy to say. However supporting the ballscrew with linear rails is going to get expensive quickly and require lot messing about.
There are ways around this thou. Use ballscrew with higher pitch and put ratio on it. This will lower the screw speed but still give desired speed.

IE: 20mm pitch with 2:1 ratio will give 10mtr/min @500rpm where 10mm pitch at 1:1 would give same 10mtr/min but screw would be spinning at 1000rpm.
This approach also gives the advantage that torque is aprox doubled so less chance of stalling motors.

This machine use the same method with 25mm 25mm pitch screws 3000mm long. As you can see in this video around min 1:50 there's no whip at all and it's doing 15mtr/min at some points.
https://www.youtube.com/watch?v=4STVbn_EMoc