How’s the fit on this shirt for an untucked button down? Should I stick with the slim cut or go to a more classic fit?

I recently ordered 2 polos from them in the original fit. Got a white and a navy one. Basically as classic as you can get. At 90 bucks each, my expectations were VERY high. What I will say is that they're different with that stiff collar and they do look nice with a blazer/jacket. What I did not anticipate though was them being a HUNDRED percent polyester. They also can't be ironed. They also can't be tumble dried. They're also made in China. I really expected a higher quality fabric (or at least a blend) and I expected they be made in the US, or at least for slightly more than 10 cents in a Chinese sweatshop. Aside from the stiff collar, I don't see what they're bringing to the table that a Ralph Lauren, CK, or other name brand polo isn't and at a third the price (or even less if you're shopping online or at an outlet store). Is it really JUST that stiff collar? Am I missing something?

I mainly live in the casual to “smart casual” territory of dressing. Here are some typical fits I’d wear. I mainly focus on basic pieces in neutral colors and getting a flattering fit in them. How can I level up color or fit wise and what colors and items would suit me best outside of the typical ? I try to keep a somewhat minimal wardrobe as you can see I’m only wearing two different pants in these photos lol.

These are my first custom made trousers and i think they turned out to be great, the rise might be tad bit lower but I'm surprised by the work of the tailor. Regarding the shirt, i didn't like it because it was light colour in the image but after receiving, it turned out to be dark. Nevertheless, i decided to pair them with creame trousers and i believe they look great? But I'm missing on the footwear, these 3 items what i have, should i wear them or do i need loafers? I'm not going to tuck in my shirt tho. Any insight would be appreciated.

What is y’all’s opinion on under shirts under t-shirts?