I'll try to answer a couple of your questions for you.

(1) Is there a website that classifies tomato varieties based on function?

No, not really as there really is no limit to the way any tomato can be used. They can fill all functions.

Any variety or color or size of tomato can be used for canning. Some of the so-called "plum" or "roma" are used by many to make sauce because they have less water in them and cook down faster. But they are not noted for their flavor so most use all sorts of tomatoes to make sauce since flavor is an important factor. It means they need to be cooked down/reduced longer but the improved flavor is worth it.

Any tomato can be sliced but likely most would grow the larger varietie, often called beefsteaks, rather than cherry types for slicing.

Color and type (determinate or indeterminate) are the 2 most important factors to most people when it comes to choosing what to grow. Days to maturity (DTM) - called Early, Mid-Season, or Late-Season is the next important criteria.

You selected 2 very unusual varieties for growing this past year, neither commonly grown so I can't comment on how they would work for sauce or salsa but very few if any varieties "comes out of the food mill nice and thick and ready to use". Reducing is almost always required.

But you can learn a great deal more about the growing aspects of tomatoes and the most recommended varieties over on the Growing Tomatoes forum here. And also check out tomatogrowers.com They sort by color, size, and DTM on their site.

As to canning tomatoes, the 'method of preparation' all depends on what you are making and is pretty much determined by the canning instructions. NCHFP and the Ball Blue Book of Canning are the basic guides to canning and tell you exactly what to do for making sauce, salsa, canning whole, etc.

is pH affected by removing skins and seeds?

No. Be sure to review the acidification requirements posted at the link below too.

Dave

Here is a link that might be useful: NCHFP - Canning Tomatoes instructions