I will be using it on paved road and off road. It will be typical countryside off-road with holes, bumps, forest roads, probably medium size stones and occasionally bigger ones, sometimes I will be riding on dirt road with dried stiffen mud hoof shapes which makes the road uneven and shaky for the rider. I will use it on mud road with dried stiffen tractor tires shapes. I will also climb and descent steep hills that are around 25 degrees. During hill descent I might ride over bumps, stones. Maybe a couple of times per year I will be using it on mountain trails and downhill on easy or medium paths. I don't know what terrain obstacles I will encounter, but since I buy a MTB I want it to be as good as my budget allows it. If I understand that some features of the bike could be useful I also might increase the budget.

I want to buy a MTB and I don't know if it's worth spending extra money on a bike that comes with a dropper post. Since I have no prior MTB experience it's hard to say what I want from a MTB. But I think that as I gain experience, my demands on the my bike will also increase. I have a more detailed post regarding some MTB models on MTB section. You're right that using only quick release on regular post on difficult terrain will be annoying but my main concern is in the case that I do it, will constantly adjusting the seat height damage the Seat Tube because of the friction ?