Alright. Short answer - use whatever works for your store. There are many different options. The regular holders should work, as long as you can lift the endcap basedeck up you are fine (as described in detail earlier). Due to how our basedecks get absolutely wrecked by the flow team, these don't work at our store since they have a tendency to pop, discolor, and snap in that environment.
At my store - as the "expert" on fixturing the "correct" labelstrip holders to use on the basedecks would be the 4ft almond adhesive. The rest of the store is to use the clear 4ft and 3ft for everything else save for specialty (freezers, pfresh cooler and coffin cases, entertainment, etc).
So, these as far as I know only come in one length. They are flexible and cut to size very easily with a blade and a snapping motion for a clean edge. So, these do have adhesive on the backs. DO NOT USE IT. It lures you in with the idea that you peel and stick and call it a day - this leads only to having almost instantaneously a missing labelstrip, or the best case scenario messy when it comes off and gets restuck on off-kilter until it ultimately falls off. They should just remove the adhesive from these - it would save me the trouble of showing everyone how to install them. They have a lip on the back of them (if you have been at Target for a while, it is similar to old style holders without the curved bottom that clear label strip holders (FX0007/fx4500?) have now - or like the freezer kind but not stiff. Anyway the back flap is clear, this goes into the bottom channel on the basedeck. Align a couple inches of this on the bottom into the basedeck channel, then (have a tool, like the black labelstrip installer, a blade, or an orange EZ remover which i prefer) and go tuck in the top of the strip into the basedeck, and go the length of the strip now. at the end, come back to the bottom, feel underneath for where it goes from being tucked in to not, and tuck that part in using the tool of your choice (fingers work too, but if you have more than a few to do, they will hurt after a while). Listen for a satisfying crackle as you go the length of the strip. Once you are done it will be flush and should be a very strong label strip - these last quite a while when installed correctly. I use these on the Infant flat as well.