NVMe upgrade for Mac Pro 4.1/5.1 Mojave

[mcnichols]

I'm hoping Darryl Ramm will be able to give some guidance here - he's hailed by many as the ultimate NVMe guru!

Currently testing Mojave on an Evo 850 APFS drive on the SATA bus in a 2009 cMP, upgraded to 12-core 3.06GHz, 5.1 firmware, HDX card/HD interfaces, PT 2019.6 Ultimate, GTX 680 Mac Edition GPU. Audio drives are spinners, but I also have other Evo 840/850 SSDs containing audio samples and older OS partitions and backups.

I've read conflicting reports/warnings about use of Trim on Mojave, and the NVMe route has been suggested since Trim support for these new drives is apparently native. So, questions arising:

1 Is there any truth about Trim Enabled being somehow 'bad' on Mojave/APFS?

2 Is there likely to be a noticeable difference with an NVMe drive (some reports suggested it might actually be slower to boot)?

3 If I do go for NVMe, what drives/PCIe cards would be recommended for this setup, and is a heatsink necessary?

4 Is it safe to leave Trim Enabled to look after the other non-system drives after such an upgrade to the boot drive?

Many thanks for any experience shared.