when I got shocks revalved from old man Hameed, they were delivered to me with positive gas charge plus the correct hydraulic oil in them, the "side effect" of the gas charged dampers you see which is self rising of the working piston was there too. According to your statement above you are assuming that your kyb are not oil filled, then you are wrong - the term gas filled shock absorbers simply means that the internal pressure of the cartridge is higher than atmospheric, this defeats any bubbles forming in the "oil" as it is squeezed through the regulator valve which is at the bottom of the working piston. Nitrogen is chosen to raise pressure because its a dry gas, no problems with moisture or reacting with oil.
secondly, you are very much mistaken by thinking that the aftermarket KYB damper units are similar to OE in performance, I say this with experience that for any brand of car - even mercedes benz equipped with Bilstein dampers - the aftermarket Bilstein damper units are not the same as the original MB items you buy from MB parts, their damping is different, so much so that they have different part numbers of the same type of strut for different sizes/specs of the same exact car.
I never liked aftermarket KYB units, their rebound damping is close to zero, the shock actually provides less than half of the compression resistance in the rebound pull, this makes for a very poor ride and can also cause "skittish behaviour" on roads. They usually end their life very young compared to Bilstein/Sachs/Showa/Tokico. The aftermarket gabriel units sold in Pakistan are the same story, no matter if Habib owns the factory and is installing these same items in their corolla assemblies - its a sort of trade inner working that 100% exact same parts like OE are never sold with another brand marking, if they are sold as OE rejects then you will see the original marking name actually ground off/painted/destroyed from the part and will be sold under the parts manufacturer brand.
in the end its your choice to spend money as you wish. My suggestion here was given on experience which I broke down as under
OE new part = major $$$$ - life 5-7 years with correct ride dynamics
OES = not available
replica (KYB etc) = $$ - life 2-3 years - incorrect ride dynamics
rebuilt OE unit = $ = correct ride dynamics (choice to have it modded to your taste), life 4-5 years.
used unit from scrap = $ - usually end of life.
This $ = is only applicable if your old units are actually OE items and not bent, dented, piston in good shape and not scratched and upper threaded area in good shape, otherwise price of used scrap parts is added - as they work on good usable core exchange business model.
I offered the above as a chart to customers, different people had different choices depending on circumstances.