I'd judge quality by color. If it's white, it's probably not that high quality and doesn't have many nutrients. If it is yellow, that's visible proof of nutrients.

Here's an answer based on my experience.

First, I eat a lot of grassfinished hamburger. When I buy the high fat (therefore, more tallow) my wife and I both noticed a kind of weird film on the top of our mouths just like you mentioned. Very odd and not something I ever notice in the regular grassfinished hamburger. And, yes, it only happened if we waited too long and it got cold. Our answer . . . we buy the regular grassfed hamburger.

Second, I use grassfinished tallow that I render myself in much of my cooking. Unlike Lard, it hardens much faster when cooled and so we need to eat it hot. In fact, in the refrigerator, the Tallow is much harder while Lard is softer. I wonder if it doesn't have to do with the higher amount of PUFA in the Lard than the Tallow, but don't quote me on that. It's just a guess. Someone on here probably knows the answer though. I've never experienced that roof-of-mouth feeling after using my rendered Tallow.

The tallow I make is usually very creamy white and, as I said, much harder to break than the Lard I render. Never used any other kind so can't really tell you how to compare. But I hope that this can help in a little way at least when comparing your tallow to mine.

I dont know the answer to your question completely but I would never just eat tallow. It doesn't really have a tasty texture like butter or lard... It's kind of waxy and strong tasting. I only use it for frying, it was also traditionally used as a fat for savory pie crusts. It's mostly best for applications in which crisco would be used. (Ewwww... Crisco)

it depends at room temperature (22 °C right now) it can be quite creamy. The whiter the fat the more stiffer it is. My yellowish fat is creamy.

The fat around organs are also more solid.

I just can't stomach tallow, if it's not fried with something, ick!

Tallow is more saturated than lard so possibly lard might work better for you if you can get pork fat to render. I render both but have never had the experience you're having with the tallow. I don't eat it straight or fry with it but I use a large amount in bean dishes and add it to stews to increase the fat content and richness. The suet is also more saturated than "back fat" as far as beef fat goes

We grow our own beef on pasture, and render tallow from the fat of animals which we have culled for our own use. The tallow is white if rendered by simmering fat and bones in water, letting it cool, then lifting the tallow off the top.

It does not coat the roof of the mouth, and tastes wonderful in food and soups. The remains (minus the bones), after simmering off the tallow, can be frozen down and used later to make the most wonderful soups, too.

Tallow from the Supermarket does coat the roof of your mouth, and this is usually an indicator of commercial processing such as hydrogenation and bleaching or the addition of hydrogenated vegetable oils. In commercial labelling, there is no requirement to indicate such adulteration. The commercial term "tallow" refers to how it looks more than where it comes from - it could be rendered road-kill and still be called tallow!

Hope this is of interest