I haven't tried all of them obviously. I've got NKP, KAS and KFS DC. It honestly depends where you plan to buy, what options are available.
I think the ones used on commercial pump boxes with stepper are KFS-ST which is a KFS with a stepper motor instead of gearbox+DC. The new KPAS-100 look nice, have a nice luer connector. KAS are nice for REALLY small amounts, like titration, for large amounts probably KCM. Honestly, NKP, the cheapeast option, work fine too if you choose thin tubing, those or clones of them are on most cheaper dosing pumps from hobby brands.
It's been a while that i ordered from them, can't find a current catalogue from them to download, last time i spoke to them the support on their aliexpress official store was helpful.
Not all versions are always available in both 12V and 24V so be aware of that. Otherwise, the tube size indicators start with a "S" or a "B" for silicone or BPT tubing, choose BPT if possible.
DONT cheap out on the motor drivers. A4988 suck and turn the motors into screaming demons. the typical 3D printer sound. The best i am aware of are TMC2209, those are the ones i use (well i use chinese boards that supposedly have genuine TMC chips, the original boards are a bit expensive), pretty much dead silent motor at low speed, you only hear the squish of the tubing.
No i don't know what the volume label does, i just ignore it, it came with the last big update i think