the de-facto industry standard has long been 'Spur' brand rails and brackets. These are usually thicker and stronger than most knock-offs. If you must use a mish-mash, I'd suggest using 'Spur' rails with knock-off brackets. Obviously you need to be sure that the brackets will fit the rails, so buy one to try first. On any given single shelf it is best if you use matching brackets, since heights vary slightly.
I note also that a tickle with an angle grinder will often make other brackets fit in Spur rails OK, even if they don't to start with.
A little reading matter here;
https://spurshelving.co.uk/Spur_spec.pdfit seems that one variable is the slot pitch in the rails; UK standard has long been 31.75mm but some knock-offs are 32mm pitch. IIRC this only becomes a problem if you want to mix rail types on the same wall; brackets from either will (or can be made to) fit.
cheers