I was running out of diskspace on my C-drive (SSD) and moved my steam library to a HDD (WD Black). I then experienced annoying short pauses when driving in areas with a lot of scenery objects. Loading some scenarios was painfully slow. Yesterday I replaced the HDD with a SSD (Samsung SSD 870 EVO) and now TS2021 and TSW2 runs so smooth and scenarios load a lot faster I know - a M.2 SSD would have been a better option, but on my mobo the PCIe 16 graphics card would be limited to 8x transfer speed if I should use the M.2 slot :-(
Yeah, moving to an SSD is a ... pardon the pun ... game changer. Yes, an M.2 NVME drive is better yet. But in a sense it's icing on the case, SSD being the cake itself. I guess I'm lucky in that my mobo allows use of two M.2 NVME drives without affecting the PCIe GPU slot. Using the second M.2 drive does entail sacrifice. It's been so long since I assembled my current PC that I've forgotten what that sacrifice is. I believe it might be that I simply can't use one of the 'lesser' PCIe slots, but don't quote me. As screwy as GPU pricing is now, I suspect it'll be quite some time before I seriously contemplate an upgrade of any sort. Normally, at about this time I'd be contemplating a GPU upgrade, but nothing affordable improves on my Nvidia GTX 1070 enough to be worth the bother.
One does not need a M.2 SSD as much as you need a SSD (though granted they are a SSD). I have steam setup on an old computer with a WD Blue 3D NAND SATA 1TB (no M.2 slot and running an old Intel I7 870), and a second computer with a Samsung 970 EVO NVMe M.2 1TB with an I7 10700F and double the memory. The jump from a 2.5 SSD to a M.2 only looks good on paper (and some benchmarks) and 'in my opinion' is not enough to justify the cost of a new motherboard with an M.2 slot, or spending much more just to have the M.2 over the 2.5 without GPU considerations (and extra cost of a heat sink if it is not included) for a gaming PC. I can barely notice a difference in load time between the two for TS21. Now moving from a HDD to a SSD, I'd pay for that any day of the week!!!
No rant... just again reminding people that a M.2 (even a NVME one) makes no great difference to game/level/map loading times. Evidence: I'm not saying that there's no need for M.2 drives... just that gaming doesn't really show a noticeable improvement with one. Given the choice, I'd still prefer a M.2 drive obviously, as many other things will benefit more. I'm really just reassuring you that you've not really missed out on anything and there's no need to worry. Your experience in TS will be broadly similar to those with a M.2 drive, and as you have noticed, either will be orders of magnitude faster than a mechanical drive. I'm not saying don't buy a M.2 drive... I'm just saying that if you have no facility to install one, don't worry... you're still getting pretty much the same experience.