But friends please tell me would taking 2 rams of same speed and configurations but 2 quantities would not cause any problems or would not at all run.
Doesn't make a difference. Ram is made from sheets of silicon. Each sheet is unique, it has different / different levels of impurities from another sheet. This greatly affects the 40+ Secondary and Tertiary timings you don't see.
You could buy 2 sticks in 2 blister packs, from the same peg, same shelf, same store, that arrived in the same container in the same box and have the exact same make, model, color, speed, timings, voltage, totally identical except for the production numbers and they could be totally incompatible. Or require massive amounts of user changes, or very few changes, or be perfectly compatible.
It's pot-luck guessing game and you are the victim. You could buy 1000 sticks and not get 2x that are compatible. That's exactly why 2x stick kits exist, the factory already did all the testing for you, guarantees compatability.
Solution: buy the full 2x8Gb (16Gb) kit you require. A single package. Then sell your old stick. Anything else means that You become the Guinea Pig, start testing sticks and hope/pray they work.
The smallest chip for DDR4 is 512Mb. That's chip, not DIMM. For DDR4, that requires 4x chips, minimum per DIMM, so the cheapest and smallest possible size would be 2Gb. If that's what you really have, 4x 2Gb, you have the cheapest built ram on the planet, in the worst possible configuration and thats not good for Any kind of performance.
Sorry.