When is water hardness a problem for hard water fish?

[pancake]

Short Version:
I see that alot of suggested hard water fish doesn't seem to go above 14 - 18 dGH online.
Are those ranges for breeding or does that suggest degrees above those numbers will cause health issues in the hard water fish?
Could bettas handle my kind of water (20 dGH) if I decided to ever get a betta?
When is water hardness a real problem for hard water fish?

More details:
Turns out my spouse wants to pick up a couple of tanks in about 2 weeks or so. I didn't expect to be getting them this soon, but I'm good with that 🙂❤️🐟
I decided to go ahead and start testing my tap water to get a better idea of what kind of fish would be good for us after we cycle the tanks.

My water went to the hardest number the test strips had, 180 ppm GH and 240 ppm KH. After the water sat in a cup for 24 hours, the ph was 8.35 according to the electronic ph meter, but the strips had a color between 7.5 and 8.0 in the 24 hour old water. I understand that ph will change once a tank starts cycling. (strips were api incase that matters at all)

I decided to do some investigative work on the GH levels in my area to get a better number. My water, which is city water, on a water quality website stated that our Total Hardness was 361 ppm where I live (which would be about 20 dGH?) The Calcium was 97 ppm and Magnesium was 34 ppm. They also stated that the ph was 7.28. I used taptool waterverse website incase readers need help if they hit the test strip ceiling too. 

Obviously, I have hard water. I don't really want to fight it. If I decide to fight my water, I would be going for a much smaller tank. I would rather work with my water. And, I am thankful it isn't higher like other cities near me are. 
I am not really wanting cichlids nor into cichlids. Snails are cool so there is that.
I did see that the Pangio Oblonga (Java Loach/Black Kuhli Loach) can handle up to 22 dGH which works for my water from what I can tell. And almost every petstore in the area sells them (petco, petsmart, I havent checked out uncle bills yet). I just don't know if the pet stores use a RO system or not. Cichlids and larger tetras, guppies, snails, mollies, little frogs, and platies seem to be common around here. So are bettas, but they are in tiny cups and not in tanks.

The store (which looks like a mom and pop place) we are getting tanks from does use RO water but they also buy fish from local people.

Looking for hard water fish suggestions to check out if you want to drop some here, and might as well ask for plant suggestions too (low light, no CO2 injections), I haven't done my research on plants yet with water hardness in mind.
Tank size is undetermined right now, as my spouse decided this week they want a stand with it instead of doing this other idea they had because this place sells them together as a kit and my spouse is picky about how it may look. I would say no fish larger than 4 inches is a safe bet.

[Guppysnail]

I’m going to move this out of photos and journals and into general discussion 

[pancake]

Oh oops! I thought I was in the general discussion after searching around the forum but I guess not. Thanks for moving my post. I'll be more careful next time.