Bathtub plumbing

[SH140]

Getting ready to relocate tub drain plumbing and have a couple concerns. I bought a drain assembly that is made of brass (which I like, it seems like it is sturdy and will stand the test of time, as there will not be access after the tub is installed). But the pipes aren't long enough for my tub and I will have to use extensions. The only "extensions I can find are either plastic or thin, cheap looking chrome-plated pipe like you see under sinks.

Which material is best for a situation like I have?

And how secure are the fittings (nut with a plastic tapered gasket) for the long term? The last thing I need is for pipes to leak after the remodel.

Thanks