May a plan provide an automatic-contribution arrangement for some employees, but not others?

A plan’s sponsor wants to provide an automatic-contribution arrangement for some specified classes of non-highly-compensated employees, but not others.  (All highly-compensated employees would be excluded.)

May a plan provide this without tripping on a tax-qualification condition?

Is it feasible to provide this using an IRS-preapproved document without losing reliance on its IRS letter?

If it's an ACA, not EACA or QACA, yes.

Thank you for the quick and clear help.

Lacking a § 414(w) “undo” distribution for those who had been inattentive makes an automatic-contribution arrangement a non-starter.

It's my view (and I've seen others within my company and elsewhere agree) that automatic enrollment is not a benefit, right or feature subject to non-discrimination testing.  So that eliminates another barrier if one implements auto enrollment for only some eligible employees in a plan.