You should not expect that brand X APs will have noticeably better coverage than brand Y APs. The limiting factors here are the laws of physics and the regulatory limits on transmit power, and those are the same for everybody. What you need if you have coverage problems is more APs.
I concur with the recommendation to look into SMB-oriented gear, because consumer "mesh" systems are not really meant for more than about two to three APs. They will happily sell you more of course, but you are paying through the nose for it because typically each unit is a full-on router plus wireless AP, with a CPU beefy enough to run a web GUI for administration as well. You only need one router and one administration point (possibly the same as the router). SMB systems are designed around those plus a bunch of nodes that do only the tasks of an access point. An SMB GUI is also likely to be more helpful for tuning transmit power levels, channel choices, and so on, which is an area you really have to deal with if you want decent performance out of a multi-AP system.
The downside though is that SMB vendors tend to assume their users are people who already know what they're doing. I'm currently using Ubiquiti gear, and I like it, but I can see that it'd be a bit of a steep learning curve for someone with little networking experience. The company's own documentation is minimal as can be, although they do have a community web forum that is full of helpful people. I'm not sure if any other brands are markedly better on that score.
I do recommend staying away from Orbi. I had a set of those about two years ago. I recall the web GUI as being clunky and not very configurable --- eg, IIRC there was no way to put the satellite APs on a different wifi channel than the primary, not that I knew then that that would be a good idea. I gave up on them the morning that I awoke to find a forced firmware update had bricked the primary router (this despite having auto updates turned off).