RAX200, RAX120 vs ASUS RT AC-5300

so you've got multiple things. 

1. Range- the broadcast power of routers is set by the fcc. And routers maxed it out long ago. So distance is fairly similar for most decent routers. Because they're all already hitting max power on broadcast. So you *might* get slighly more range but it isn't going to be significant

2. concrete. in apartments concrete kills wifi. it is literally one of the best blockers of wifi. nothings going to penetrate it well. 

3. apartment living. tends to have many more wifi signals which cause interference. Maybe the RAXE500 might help with the move to 6E to reduce congestion but if you're having congestion issues in 5ghz, you'll continue with most devices. 

4. A move to a bigger home. 5000sq ft is huge. I don't know of a single router solution that'll fully hit that range. If you're looking at upgrading, I'd do your best to stick it out with the router you have and upgrade to a mesh solution (triband for that size) when you move. Or buy the mesh solution now and only use the router part of it. But you'd be better to wait as prices always drop with networking gear. 

With what you have going on, I'd wait on purchasing a new router until you move. A router that's going to work great for an apartment, isn't the same router that'd work best in that size home you plan on moving to.