The first one is a print from an etching by Mary Clark Ellsworth. She was born in Altadena, California on 3rd October 1882, lived most of her early life in Hawaii, and then moved back to California around 1915 where she was active with the Palo Alto Art Club for some years. She died in Glendale, California on 14th January 1971.
I think your print dates to around the 1950s and at that time she was producing work for the Barlow Advertising Agency who used her prints for greetings cards and the like. She was also a prolific illustrator for young chidrens’ books, producing charming works in both line-art and watercolour.
As you suspect, these prints are not of any real value… there’s a pair of them here that went for $10:
https://www.ebth.com/items/6169191-m-ellsworth-english-abbey-church-and-cathedral-engravings
The second item looks like a department store wall art print. Maybe you could track down the original artist, but it may just be a commercial studio. The fact that there’s no signature should tell you it’s probably not worth tracking down.
Difficult to tell from photograph alone, but the third item seems to be an original watercolour on textured art paper. Personally, I would say it’s not from a skilled artist and looks like some of the native work I’ve seen on sale at tourist markets. I actually rather like it, but wouldn’t think it valuable. Again, no signature is probably a bad sign.
