Airport 5ghz confusion

Hi there! Im going nuts with my airport setup. I recently moved, and while I pay for 200 mbps service, with wifi my top speeds are 120 average if Im sitting in the same room. I get insane fluctuations. The next day I may get only 40 mbps. And the rest of the house averages 40 max. So I tried switching to strictly 5ghz with my AirPort Extreme. The speeds are now a solid 120 through the whole house (I use another extreme for wirelessly extending to the upstairs). But for some reason I only show 2 bars. I have a couple apps that say no wifi, even though my speed test show 125 mbps. So today I hooked another extreme up to wirelessly extend to my living room. Now the 5ghz network shows 3 bars, but my speed tests are around 40. This doesn't make any sense to me. Any ideas? Im trying to just keep everything on the 5ghz network as it seems to be way less crowded and faster, but we listen to music in the living room through our phones apps and the apps won't connect for some reason. I just don't get why my iPhone would show 120 with 2 bars and 40 with three?!?!?