An end cap will look like the end of a breadboard. The reason this is done is to cover the end grain and to keep the boards from twisting and splitting. A spline can also be put in the end to serve a similar function although the end grain would still be visible. You could also just nail a thin strip of wood to cover the end, but I would consider this poor workmanship unless the top is made of plywood. A thin cap would be ok, as long as it is mortised into the end.

You have to be very careful how the cross grain piece os attached.

It should not be fastened the entire length to allow for the movement of the wood as moisture content varies through the year.

Most higher end tables do not have this type of construction.

The end grain shows, but if the wood is matched and finished correctly it is not bad looking at all.

Every bread-board end I've seen has been on the short edge of the table. That is, the main boards run the long dimension of the table and the bread boards the short way. I would consider tables made this way to be rather "casual," sometimes called "farm tables," "tavern tables," or the like.

It will not stop the main boards from moving with absorbing or desorbing water vapor seasonally. Depending on what species of wood, how the annual rings are oriented, and how wide the table is, it would not be unusual for the wood to move up to 1/2", while the breadboard end will have practically no movement in that direction. So there will almost always be a "step" at the point

i concur with brickeyee
An experienced WW ,( not even an expert ) should be able to join a table top without what some call a " barbers pole " look .Some woods are a little more difficult to finish the end grain but I feel the end grain not only looks good but can enhance the joined piece .I think bread board ends are meant for more " country style "appearance. If that is what one wants then fine. There do not need to be definite lines as one views the joined boards from the ends. The boards I join look like 1 piece of wood.That is not meant as a brag . Happy wood working. Johnny

I used a wood end cap on a kitchen countertop. I posted photos in that discussion. It's in this forum and I think the title is somethink like "Wood Kitchen Counters". The wood I was working with was tongue and groove flooring so I had to either do an end cap or remove all the tongue and grooves and join the wood flush. Maybe it is a sign of an amatuer job but I was happy with the look. In retrospect, it might have looked better if I had done a dovetail join at the corners.

Artisan joinery has been appreciated for thousands of years, because of its simple demonstration of how furniture is pieced together by interlocking the wood. The main woodworking tip is to focus on the type of joinery you will incorporate in the table design and make it a goal to not use any adhesives. Instead use clever, attractive wood joinery to add subtle elegance to the central focus of your dining room.