Intel & AMD MacBook Pro had better monitor support than M-Series MacBooks

[pshufd]

I was able to drive four displays with my 2014 MacBook Pro (the internal plus three externals, including one 4k), even though that exceeded Apple's stated specs. So I suppose it's possible I could drive a third external on my 2019 iMac using the HDMI output....

I was able to do that as well on my 2014 MacBook Pro but there were limitations on resolutions and maybe frequencies of the external monitors.

I find that running 4k monitors off the 2014 and 2015 MacBook Pros really get the fans spinning. They don't have problems with 2k though.

The Intel Integrated uses system RAM for video memory and running heavy memory-intensive workloads could result in screen artifacts. A dGPU was a lot better in this regard.

 

[theorist9]

I was able to do that as well on my 2014 MacBook Pro but there were limitations on resolutions and maybe frequencies of the external monitors.

I find that running 4k monitors off the 2014 and 2015 MacBook Pros really get the fans spinning. They don't have problems with 2k though.

The Intel Integrated uses system RAM for video memory and running heavy memory-intensive workloads could result in screen artifacts. A dGPU was a lot better in this regard.

My 2014 MBP is the 2.8 GHz model, so it has a dGPU. I ran a 4 k + 2 x 2k, all at 60 Hz and full resolution, without any artifacts. But yeah, it did get the MBPs' fans going, since anytime you connect an external it defaults to the dGPU. And if the room was warm (> 80F) I experienced thermal throttling unless I blew a fan continously towards the back of the laptop (which I did using a very quiet button fan set on low).

 

[pshufd]

I was able to drive four displays with my 2014 MacBook Pro (the internal plus three externals, including one 4k), even though that exceeded Apple's stated specs. So I suppose it's possible I could drive a third external on my 2019 iMac by splitting one of the TB3 outputs...

I have the 2015 with the dGPU as well and it runs warmer than I like with 1 4k monitor.

I used to use a 165 CFM twin AC fan setup and it blew a lot of air on the bottom of the laptop but only lower the temps about 12 degrees. The 2021 MacBook Pros can run my workloads with external monitors at ridiculously low temperatures. But I ordered mine with the M1 Pro as I didn't realize that it only supported two external monitors. I assumed that it would support three like the earlier MacBook Pro 16s. I was in a hurry to order as I worried that they would quickly go on long backorder.

Getting the dGPU or the higher-end GPU could give you some additional functionality. There are limits on some of the older iMacs but you may be delighted that they can do more when you actually try it.