Both Okna and Soft Lite are much better performers. In fact both of Okna's and soft lite's budget lines are better than plygem 5000. Plygem also use a
Tin plates spacer system calles intercept. Okna and soft lite use non metal spacer systems. Both also have very low air leakage numbers as well.

There are several brands that will meet your performance requirements (i.e. being a solid extrusion and air tight).

Okna is one of them as is Soft-Lite, Sunrise, Slocumb, Affinity, etc.

Not all Soft-Lites come with a non-metal spacer standard but it is an option on all.If you think the 5000 is flimsy I'd avoid the Soft-lite Barrington as well.