"How about a bag like this?"
So, I totally overthought this sentence. It's not specifically asking if you want a similar bag to this bag. It's just plain asking "how about this" or "how about this bag." The implication is that one is picking up or pointing at the bag and saying the sentence.
It's the "how about" part, you're asking about someone's opinion on something. いかがですか? is like "how is it, what about it" or a simple "so?"
Ikaga is more polite than dou. For example: Ikaga could (and should) be used by a waiter who asked you how was the food. Dou could be used by your friends asking how was your weekend
Can you say something similar like what's up or how you are doing instead of just genki desu ka?
"Choushi wa dou" is one less formal way I know of, but I think a lot of slang is very contextual, so not sure it would be used in all of the ways we say those things.
I've read that 如何 is more commonly spelt in hiragana いかが, that the kanji spelling is rare.
Konna means like "such a". Konna utsukushii onna Such a beautiful woman