I live in the PNW, but I hadn't worn flannel/plaid shirts since the 90s until I added a couple in the past year. I have them now for a few reasons. One is because they do suit our climate very well as layering items; I usually wear them over a T-shirt of some sort. Another reason is that for me, who grew up in a dressier environment, they serve well to dress things down in a way that suits this area and my lifestyle better. For example, I find pairing a plaid shirt with a skirt more interesting and less dressy than, say, knitwear with a skirt.
As for what I look for...I prefer a combination of good quality and what I consider a very reasonable price if I can get it. One can pay more than $100 for a flannel shirt as you show (hmm...that one is rayon), especially for the wool ones. Many of us appreciated the quality of the wool Pendletons that we used to score for less than $5 each at thrift stores in the 90s. Then the vintage clothing craze really took off, and you couldn't get them for less than $25. New ones can be almost $200, but Pendleton's aesthetic can be very harmonious compared to others.
For another take that is unconcerned with current fashion trends but in a different direction, here's a more...Americana-oriented outfitter. As with many things, one can sometimes find value by going toward the source of what inspires premium-priced fashion. One of my shirts is a Carhartt.
Speaking of which, I myself look specifically for shirts that do *not* have a regular pointed collar, for reasons. I have either hooded ones or "mandarin"/collarless ones in this area.
Another thing I look for is lower-contrast plaids, because I find that on me, a petite, some patterns can overwhelm. My personal taste also rules out shirts with a lot of white in them, pastels, bright candy colors, buffalo checks (I think just because been there, done that), and, believe it or not, the combo of red and blue--which is probably the most common one found in plaid shirts (I seem to have a poison eye for the combo in most instances, not just plaid). Let's just say I know what I like...but I can be a style outlier on YLF.
There are a LOT of cheap, cheesy, low-quality plaid shirts out there these days, especially in the juniors space, so I don't know if I'd even try one from H&M even though I do buy other things there.
I know, loooong post. I'm an analytical person, what can I say...
