to my opinion you can better invest in 512GB Ram memory than in m2 nvme drive.
I would say it depends on the volume you are looking to plot.
A decent US$200 --> 300 nvme drive, an adaptor for it if needed and 128GB ram can give a plot every 34 mins or quicker with old server hardware. For 100TB written not one NVME failure yet although. I use MadMax with tmp1 as the NVME.
If you are likely to get through a lot of NVME drives due to the amount of plots you are creating then 512 GB ram is a good option but that size of ram is pretty expensive. If Chia was still at US$1.5k pre coin then sure, but now with the current pricing.....
Small SAS drives are cheap but take more power, generate more heat, require SAS connectivity (adaptor, cables etc that home users may not have) and tend to be slower unless runing large arrays. I have 24x 10K drives and put some timings in the Chia Farm thread when MadMax came out.
I also used 4x HGST 400GB SAS SSDs raid 0 (cost around US$250 for all 4) for a while which were good speed wise but needed the drive bays for storage drives so went back to NVME on a PCIe adapter in the end.
I prefer to go with used enterprise drives as they are generally well tested and have a fair amount of knowledge floating around the internet by the time they reach ebay. Of course it is a bit pot luck on if you get a good one (lightly used) or not. I seem to have been lucky on all but a 6TB drive so far. New products, first gen, tend to have some kinks to work out especially if they are rushed to market.
If you do go for an NVME drive, check if they are using a small DRAM cache as you will get good speeds for standard use most of the time but for write intensive use like plotting, the cache will run out fast and then you drop speed quite badly. Hunt for spec sheets, try and find reviews etc and you should be ok.
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