Yes the SSD did need to be formatted to make it its own drive. Getting to it to replace it is too difficult.

The whole point of this guide is to add a drive, not to replace one.

Correct. This is a Fusion Drive, but I was only bypassing the spinning disk part. I still had access to the tiny 128GB SSD inside.

The SSD’s haven’t really changed. I would just get the latest that Samsung makes like the 870 Evo. https://a.co/d/aSIIg5L

You can buy any size SSD you want as long as it's a SATA drive. Good luck!

It was great for me. Mine was 128GB which was perfect to use for Boot Camp Windows install.

Yes, the factory installed PCI drive is accessible at a second drive when you replace the HDD. You then can format both drives and use them as individual drives.

I don’t think so. Even if there was an adapter you would lose all the benefit of an NVMe drive, which is it’s speed.

Correct. I only replaced the tape on the top and sides. I did not cur or remove the tape on the bottom, no need to.

So it all depends on the drive you install. I typically use Samsung 860 Evo for my installs, and that’s what is in my iMac. You speed tests are going to be off with a Fusion Drive, since you have both an SSD and HDD. Those numbers you are getting are based off your SSD, but your real world usage will vary. Since a speed test, like Black Magic, can target the SSD or macOS partition, the speed test will look better than it really is. With a Fusion Drive macOS is on the SSD but all your apps and data are on the HDD, for the most part. Apple does move things around a bit, but more or less that’s how it works.

That being said my benchmarks are about 500 write and 1500 read. Either way, I’m very confident that you will see a huge performance boost in app launch and data transfer by swapping out the HDD and replacing it with the SDD.

Personally I would buy an 860 Evo, don’t waste your money on a pro.

https://ssd.userbenchmark.com/Compare/Sa...

Yes the SSD option is still great in 2021. And yes just run internet recovery, format for APFS, and install Big Sur. There’s really no issue if you’re doing a clean install.

Doing the PCIe install is a MUCH harder and longer procedure. I would not recommend it.