I have tried to experience atmos using a pair of old stock speaker from an HTIB. Had used some aluminium strips to fix them to the ceiling , as I was unable to resist trying the atmos experience with my new AVR. Here are my comments
1, Its not easy to fix something to a false ceiling, as it will easily get detached due to the nature of the ceiling tile

2, Atmos speakers are not just gimmicks, it also does the hardwork like your surrounds
3, Use a matching speaker to your surround, it maybe better to do a timber match with your surrounds than going for a totally different one
4, ofcourse you will need a strong speaker. A spare one like what I used, may not do justice to atmos experience
5, If you can, go for 7.2.4 setup. I could understand how atmos tries to shift soundstage with just two overhead speakers, but 4 overhead speakers will be great (ofcourse will offset you by another lakh or so

for the receiver )
6, Audition top firing, front height speakers before you opt for them. Ofcourse it is simple and clean but in my opinion, can never replace an overhead speaker experience
7, Unless you already have provision for overhead speakers, your atmos wiring is going to be a mess unless you are a professional or hand it over to professionals
8, I found the atmos demo disc as well as the mad max fury road, very engaging which really gave me goosebumps. On the other hand, some hyped atmos/DTSX movies didnt met my expectation except occasional drizzles/bird chirps/footsteps etc
9, If you can, upgrade to atmos right away. It is indeed a different experience to enjoy. I will say it was better than what I experienced in couple of movie theaters, but its purely my perception
10, Try to move your seating position few fits forward or backward, something like a subwoofer crawl. It gave me better experience after slightly adjusting my seating position