As mentioned previously, I got a good deal on used M1 Mac mini with 1 TB SSD and 16 GB RAM. However, this deal has cost me another CA$1000 (US$735) plus CA$207 (US$152) plus tax.
My previous 2014 i5 Mac mini had a decent amount of ports, but the new 2020 M1 Mac mini has fewer, so I spent another $207 to get a Plugable Thunderbolt 4 / USB 4 hub to compensate. However, Apple Silicon's implementation of USB-C / DisplayPort Alt-Mode has caused all sorts of compatibility problems with 3rd party monitors, and even with Apple's own older monitors that are no longer supported.
I had a 30" Cinema HD Display that behaved well with my Intel Macs (eg. 2017 iMac, 2017 MacBook, 2014 Mac mini), but which had all sorts of problems with the M1 Mac mini. Sleep stopped working properly with some adapters, some adapters didn't work at all, and HDCP stopped working for some strange reason. Because of all this, and because the monitor has some image retention, I finally just got a new monitor. Or several new monitors actually.
I started with an
Asus ProArt PA328CGV. This is a 1440p 32" monitor (92 ppi) and I was running it at native 2560x1440. Text in a Windows VPN was crisp but pixelated at my seating distance, and it was blurry in macOS. BTW, this monitor is an HDR600 monitor which looked good, but which I ended up not using HDR. The 165 Hz support was a nice bonus though. 165 Hz is not critical, but screen navigation was considerably smoother than 60 Hz. Actually, I didn't notice much difference between 165 and 120 Hz though so I ran it at 120 Hz. This monitor is factory Calman calibrated and colours look great.
Even though my previous Apple Cinema Display was only 2560x1600 (101 ppi), that slightly higher rez plus the slightly smaller size at 30" made it a little harder to see the pixels (although it was obvious a little bit closer).
So then I ordered a higher rez model from Amazon Warehouse, an
Asus ProArt PA329CV. This is a 4K 2160p 32" monitor (138 ppi), but I received another PA328CGV in the box. It seems like someone scammed Amazon Warehouse by buying the PA329CV and returning a PA328CGV. So then I reordered it retail from elsewhere.
I just got it today and I'm currently also running at "looks like" 2560x1440p. In this mode, macOS text is considerably better, decent, but not awesome. Text in the Windows VPN is also decent. I tried at "looks like" 3008x1692 and while macOS still looked relatively OK (albeit with smaller fonts), the Windows VPN text quality took a nosedive. I tried turning off font smoothing, but while the text in macOS was crisper, it also thinned some fonts making them look a bit anemic, so I'm back with font smoothing back on. BTW, this unit has a bit of backlight bleed but at this point I can't be bothered to get another one, especially since AFAIK it has no stuck pixels. This is an HDR400 model and interestingly Apple doesn't allow HDR on this model, which is fine, since HDR400 is kinda pointless anyway. This is also factory Calman calibrated and again, colours look great. I'm running this monitor through the Thunderbolt hub too. I'm sticking with this monitor, but it's definitely not the perfect solution for a Mac mini. One interesting tidbit. The monitor can act as a USB hub, but there are settings for USB 2.0 vs. USB 3.1. If you set it to USB 2.0, macOS gives you 5 default scaling options up to full 3840x2160 at 60 Hz. If you set it to USB 2.0, macOS gives you 4 default and less flexible scaling options up to 3200x1800 at 60 Hz. I guess the USB 2.0 setting frees up more bandwidth over that USB-C cable.
I also have a 2017 5K iMac (218 ppi) running at native "looks like" pixel-doubled 2560x1440 and while text is amazingly crisp, I find the default font sizing too small. If I decrease the "looks like" resolution, text is way too big and there is not enough screen space. For the same reason, I don't want to buy an Apple Studio Display. It's expensive, for a too small 27" size at 5K IMHO. I've said this before, but I'd love to be able to buy a 30" 5K 16:10 or 5K 16:9 monitor. That would be awesome. The 32" 6K Pro Display XDR is far too expensive and is way overkill for my usage anyway.
My holy grail would probably be something like an ultra wide 6K at 33" with a resolution of 6016x2880 (202 ppi), with 120 Hz support, but that would likely take an M3 or M4 or something.
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tl;dr:
M1 Mac mini is a disaster for monitor support, but a lot of you knew that already. For text quality:
30" 2560x1600 at 2560x1600 - 101 ppi is OK. Not great but acceptable text.
32" 2560x1440 at 2560x1440 - 92 ppi text is blurry and pixelated.
32" 3480x2160 at 2560x1440 - 138 ppi is decent, but text looks a bit soft.
324" 3480x2160 at 2560x1440 - 138 ppi with font smoothing off looks crisper, but some fonts are too thin looking.
32" 3480x2160 at 3008x1692 - 138 ppi is OK but Windows VPN text quality is noticeably worse.
27" 5120x2880 at 2560x1440 - 218 ppi looks great, but the default font sizes are smaller than my preference.
I'd like to see a 5K 30" at 5120x2880 - 196 ppi, or 6K 32" at 6016x2880 - 202 ppi. Text would be excellent.
120 Hz at that high a resolution would probably take an M3 or M4, but 120 Hz isn't mission critical.