At the time, I thought BELLA+CANVAS only sold wholesale, but I now see a retail section on their website!
I really like the comfort colors heavyweight ones personally - this seems to be the one in my order history. They are plenty soft once you wash them especially if you run a few cycles with some fabric softener. The price isn't amazing right now (my history says $6.50-8 is more typical) but the site ships fast and doesn't care if you're commercial or don't want logos etc.
https://www.jiffyshirts.com/comfortcolors-C1717.html?ac=Whit...
I used to get others but most of them are too scratchy or bad in some other way. I used to still get them "because they're free" but what's the point if I never wear them? I do have some extra large but scratchy shirts that are tolerable to wear.
I have a really good Datadog shirt that's not Bella+Canvas.
There are a variety of mid-level T-shirt brands (such as BELLA+CANVAS) that feel so much softer against the skin, no irritating seams, stand up to repeated washings, and are lighter-weight, meaning you can wear them as-is in the summer months, or under something else in the winter months, and it feels comfortable either way.