Any window can be installed as a "full frame" in this case and the UltraWeld is not unique in this capacity. It is a bit on the hefty side so depending on what kind of windows you have, it may result is a net smaller glass size, but usually if you are doing a full tear out, that mitigates or eliminates that differential.

What kind of windows are coming out?

We bought the house last year and the windows are original from 1990 with no visible branding on them that I can find. On the inside they're a honey oak look and on the outside they look like white aluminum. Vast majority of the windows are casements with only two picture windows.

Is that the info you're looking for when you ask what kind of windows are coming out? I also don't know if I'm using the terminology correctly, when I say full frame I'm talking about tearing everything out down to the 2x6 opening or maybe said another way, leaving nothing from the previous window install behind.

I can post a few pictures of them if need be.

I should also mention that the second installer said the UltraWeld couldn't be installed as a full frame replacement because there's no nailing flange or the like.

The ThermalWeld Plus is there only option with nailfin now.

Is the ThermalWeld Plus the same/similar performance as the UltraWeld?

when optioned the same they are.

Sounds good, the primary point of my original question was to make sure that I wasn't getting a lower end/mid model of the brand if I ended up going with the ThermalWeld Plus.

Do your windows have trim/casing on the outside?

This is from my bathroom but is pretty representative of the entire house. Vinyl siding and what looks like gel coat stain coming up.

You will have to remove some siding to use a nail finned window

Would that be a cause for concern or even a significant amount needed to be removed? Also does that usually drive up cost by a meaningful amount?

You have to remove enough to access and have clearance for the nailfins. The cost can go up a bit. Your sales person is the one to talk to. This type of installation is one of the more costly and detailed.

Am I correct to assume the only other option is to do an insert which would reduce the amount of glass by a few inches width wise?

Few inches...not likely. It's not terrible hard to do the comparison math if your installer can just show you what the mock up differences would look like.

They could do a full frame without nail nail flange and and out ut into the rough opening or do as insert and put inbetween tour interior wood casing, this would give mire glass loss. From the edge of the frame to the edge of glass will be roughly 3”.