Solid window. Standard size can be a bit all over the map as well as installation pricing due to the homes construction. Is the installer doing the demo? Siding type? Age of the home (lead paint)? Interior conditions?

Siding type: Wood

Age of Home: 51 years

Interior conditions: clean?

No demo. Replacement windows.

Other than the 3 bathroom windows which are smaller, the rest are about 5.5 feet by 3 something feet?

Looking for black exterior, grids (gdg) on top sash only.

By replacement I assume you mean insert windows (reuse existing frame) or are you going for full framed replacement?

Yes that is correct. Replacement. As in will be using existing frames.

As of right now I am debating between Marvin Essential, Marvin Elevate, Okna 500 and Okna 800.

Hard to predict pricing but the Elevates should be the most since it would cost extra to have the interior prefinished from the factory or afterwards. Best bet is to get a few bids on each and decide from there.

Following... also looking at Essential line. We like the modern thinner look and the all fiberglass (rather than wood interior). Wondering if essential is a good product (heard some sales people telling us it was 'builder grade' as if that is some kind of lower quality thing?).

I think it is a good product , I think for some the looks might not fit the term but that is mostly subjective.

Did anyone install the Essentials line? I was holding off on windows but now found a leak with wood rot, so will need to make a decision. Would love eedback from those who have them.

Installed plenty of them. Decent window. If you want that thin and modern profile, and you can't use aluminum, this is a fine option.