To be honest, I don't think it's about having dog experience, so much as being willing to put in the work!
I have a working Cocker, and he's hard work but amazing. I love him sooooo much. Mine is fearful and reactive, though; and really, it's mostly this that's difficult. In terms of his general "fizzy, busy, Spaniel-ness", I'm used to that now. It was a shock at first, how clingy he is, how energetic, etc., but he's so fun, and so loving, and so clever.
He knows about 50+ tricks and commands, can fetch his toys by name and even colour, has a fantastic understanding of vocabulary, brilliant recall, and is very well trained. I've put in a lot of work. Easily a couple of hours per day, between exercise, mental stimulation, training, etc.
I wouldn't say working Cockers are easygoing dogs. As in, if you skip a day's walk, get sloppy on giving other activities like sniffing games and training, etc., you'll probably know about it very quickly. But if you're able to devote say 2-3 hours a day on average (with half of that being training and mental activities), you won't really have a problem.
I've often wondered if I'd be happier with a lower-energy dog. But I've also asked myself if such a dog wouldn't be so fun and engaging.
As for being left alone, mine has no problems! It's more about training, usually. He was left alone frequently from the day he came home, so it became totally normal, no big deal. Just 10 mins here and there, then an hour, then more, etc.