Money is not a problem but I do hate spending it on overpriced goods. I would go as high as 500$ for a smartphone, everything above that seems a bit crazy. Can't have a phone that is more expensive than your avg PC.
Google pixel is also interesting, OP5 too, like I said there are so many good choices out there, it is hard to make a correct call. But there are no huge differences among all those models, so in the end pick one and you win it seems :)
For 500 dollars, depending on where you live, I think only the OP5 falls in that range. I'm in euros, so I don't really know the prices elsewhere. IPhone x, and pixel will set you back around 1000. I'm assuming you will buy the phone outright?
There are several options with the providers, all those options and phones from their stores are more expensive than for example ordering those same phones from amazon. I'd rather buy one outright.
Yes, good idea. It is much cheaper in the long run. Just make sure the bands that your carrier has are supported by your phone (keep in mind some phones have different variants).
At the moment, pretty much every flagship phone is pretty decent. You only have to be more careful at the mid and low end. Samsung is supposed to be good, but with heavy skinning. It just isn't for me.
btw, iPhone and all the Apple products are overpriced, I can tell you that (typing from my MacBook Air). No, but really, you pay for a brand and half of the options they have, I rarely or never use. Be smarter :D