When you are not reloading....you use what ever comes in the box. Everyone seems OK with that until it comes to reloading.
It is amazing checking the COAL (cartridge over all length) from one brand to another. With basically the same FMJ 9mm shape, the length can vary quite a bit. The actual bullets are the same and definately not enough of a shape change to merit the COAL changes. When using different bullets where the shape does vary quite a bit (like Hornady XTP) it is best to start with the mfg. recommended COAL but maybe check the actual distance the bullet will chamber from barrel rifling in a particular gun. Since you are reloading for several firearms, you will need to possibly compromise to something that works in all guns. This is where so much confusion comes in and of course nobody wants responsibility should you make a mistake.
I have started using Power Pistol in 9mm. Was using W231 but only because it was on hand for .45ACP reloading. Power Pistol lets 9mm get to a higher velocity than W231. It appears starting in the middle of recommended charges works without a problem, and skips the cycle issues in auto firearms that haven't been modified for light loads. (yeah, expect some FTF/FTE issues with light loads unless recoil springs are changed).
Hunting around on the web can find lots of gun specific loads. Powder companies have online load info you can print, download or have emailed to you (don't know why there are so many options, most likely responsibility concerns). Powder manuals are available at most stores that stock powders. There is a pretty decent booklet you can find at most places selling reloading supplies that is a binder of various reload data that is pretty decent. Then there are reloading books that come in handy if you are going to use certain brand bullets.
Lacking a way to test pressures, you will have to pay attention to pressure signs (primer shape after firing, case issues, embossing). A chronograph will be a good investment to really understand what you are getting in different guns. Finally will be the results on targets.