I recently bought a 256GB Galaxy Book Pro 13.3 (model NP935XDB) with a 256GB SSD but wanted more capacity. The SSD is the 2230 size which isn't very easy to find with 1TB capacity. After much searching I found that Dell UK (as that's where I live) were selling a Dell branded 1TB 2230 at a relatively reasonable price (about double the cost of an equivalent 2280 SSD). The SSD I received is Kioxia (who bought the Toshiba SSD business) with a Dell part number on the label.
After cloning using Macrium Reflect with the new SSD in an external caddy, I opened up the Samsung. The first step is to remove the screws under each of the four rubber feet and then peel the palm rest and base apart. This process is probably most easy started at one of the front corners after which it's a matter of working along the joint using a spudger or strong thumbnail to separate the plastic clips. Once the base (amazingly lightweight) is off then the SSD is hidden under the silver cover. The yellow label contains a reminder to disconnect the power adaptor and disconnect the battery (prise the connector upwards from the socket). Care is needed to remove the cover over the SSD. I used a very small flat-bladed jeweller's screwdriver poked into the small gaps at each corner of the cover in turn to carefully lift it while trying to not bend it out of shape.
The SSD swap was then easy - remove one screw, slide out the old SSD, slide in the new one and replace the screw. Refitting the cover was much more time-consuming as the bottom of each side sits in some very narrow metal grooves and getting everying lined up and seated isn't quick. I wonder what the cover is for? Is it radiation shielding? Something thermal would normally be black although if it's in contact with the computer base then colour wouldn't matter (but why not use a thermal pad?). I then reconnected the battery and checked that the computer booted OK before shutting down and refitting the base.
In addition to the extra capacity there's also a speed boost. CrystalDiskMark shows the speed of the 1TB for most tests to be about 20% higher than the original Samsung 256GB PM991a SSD but, for some reason, Seq Q32T1 writing is higher by about 60%.
Samsung PM991a 256GB
Sequential Read (Q= 32,T= 1) : 1980.763 MB/s
Sequential Write (Q= 32,T= 1) : 1116.577 MB/s
Random Read 4KiB (Q= 32,T= 1) : 501.342 MB/s [122397.9 IOPS]
Random Write 4KiB (Q= 32,T= 1) : 495.957 MB/s [121083.3 IOPS]
Sequential Read (T= 1) : 1269.407 MB/s
Sequential Write (T= 1) : 1154.674 MB/s
Random Read 4KiB (Q= 1,T= 1) : 43.412 MB/s [ 10598.6 IOPS]
Random Write 4KiB (Q= 1,T= 1) : 164.910 MB/s [ 40261.2 IOPS]
Kioxia BG4 1TB
Sequential Read (Q= 32,T= 1) : 2377.243 MB/s
Sequential Write (Q= 32,T= 1) : 1833.285 MB/s
Random Read 4KiB (Q= 32,T= 1) : 616.300 MB/s [150463.9 IOPS]
Random Write 4KiB (Q= 32,T= 1) : 503.722 MB/s [122979.0 IOPS]
Sequential Read (T= 1) : 1438.888 MB/s
Sequential Write (T= 1) : 1382.293 MB/s
Random Read 4KiB (Q= 1,T= 1) : 59.772 MB/s [ 14592.8 IOPS]
Random Write 4KiB (Q= 1,T= 1) : 193.423 MB/s [ 47222.4 IOPS]
Nothing else is upgradable on this notebook. I would have liked 16GB RAM but , in addition to being somewhat more expensive, they are in the mystic silver colour scheme and I know from past experience that those keyboards are less easy to read as it's white backlit lettering on a silvery background. Samsung should be more innovative here. How about mystic maroon?