Thought I add my experience after getting all the information for swapping the disk from this thread.. As a small payback I guess:
Got a mid 2014 MacBook Pro DG, at the time top model. For a long time already I knew the battery was no good (swollen), so started searching for a replacement.
As well, the screen has the dreaded damage from the reflective layer issues. Not a big issue during use, just irritating to look at when it's off.
Then a 2015 MacBook Pro IG came in at work (working for a recycling company) with no HDD but the rest in perfect condition. So I started researching for an SSD as well.
Ordered a cheap battery replacement for my 2014 MBP and cleaned out 6 years of dust.
Ordered 2 cheap Chinese adaptors. Thought since I have to wait for delivery, better order 2 in case one gives problems.
Full sized Adaptor
Small sized Adaptor
Searched for a good SSD based on the tables at the start of this thread and decided on this one:
Adata XPG SX8200 Pro 1TB PCIe Gen3x4 M.2 2280 R3500/W3000MB/s.
The battery I ordered for the MBP 2014:
MPB 2014 Battery
No good, followed all the instructions that iFixit recommends, fully discharging, then charging with at least 2 hours longer on power, etc.. But the battery indicator falls from 60% suddenly to 7%, even though the battery will then still have like 2 hours charge available. I can live with that, mostly working on power-adaptor anyway, and for that price, it's better and safer than the bloated old battery.
So when the adaptors came in, it turned out that the ADATA does not fit in the Full Sized Adaptor. The SSD is populated on both sides and the connector is too low to accommodate that.
The Small sized adaptor did fit without a problem.
Installed the Adata SSD in the 2015 MBP and closed it up again, I used a USB install disk for Catalina. All went very fast and easy.
Finished installation, downloaded Black Magic Disk Speed Test and wow..that Drive is fast!
So since I still had the the other adaptor, I just took my external backup drive (Crucial 1TB P1 NVMe M.2 SSD), emptied it on the 2015 MBP, and emptied my 2014 MBP as well, took out the original Apple 512Gb SSD and did the same installation process.
The Crucial is populated only on one side, so no problem fitting it with the long adaptor.
The 2014 MBP is slower of course on the SSD bus, but I still went from 600-700MB/s to 1400/1500MB/s. Need to check that once more at home.
Both SSD show as 4 lane links.
The 2015 MBP info as per below, link-speed at 8.0 GT/s
The 2014 MBP has a link-speed at 5.0 GT/s
Up till now, I've not seen any issues with heat. Battery temperature is slightly higher at 31'C vs 29'C before the swap.
No issues with sleep that I've noticed on the 2015 MBP. I've not changed anything on hibernation or sleep settings. Clean install and left it like that. It's not been off since Sunday and I just close the lid in the evening and start working in the morning.
For the 2014 MBP I still need to check a bit more on that, but during use on Sunday and some testing with closing the lid for a while, no problems at all using it.
Very happy with the work done on both. No issues and no problems, easy and quick to do.
Below a picture after I opened the 2014 MBP the first time.. yikes..lol..
Well, the bloating did make removing the battery very easy...
Happy to provide more information if someone likes to know. Just drop a reply.
Cheers,
Luc