Unfortunately, airsoft is still very much a hands-on and unregulated hobby. Like with biking (as I do myself), most things are "good enough" but not great out of the box. You will often have to spend more and tinker yourself to tick all the boxes you are after. There are an unbelievable amount of trash copies of trash copies of trash copies out there, and usually all copy the same design flaws. Best to ask before buying because it is a minefield out there. You'll be surprised at how many people say "I already bought X, is this a good gun?".
The customer service and warranty you are looking for will mostly be from the retailer you bought from, not the brand itself. Patrol Base is usually a good place to start. The brand label usually won't give two shits about you. That being said, of course, not all brands are equal. The only brands that I can confidently recommend out of the box are CYMA Platinums, Arcturus, and G&G guns right now. Other brands usually have some cut corners that end up exploding if you even attempt to change anything, including the spring, such as brands like NUPROL and Double Eagle from my experience.