Choosing New Router & AP Layout - Setup & test without internet connection?

Hi all! I'm moving into a new apartment in a few weeks. It's 10.5m long (4.5m wide so no concern about coverage there) plus a 4m deep balcony at the end and there's a second floor with two bedrooms. So basically a townhouse style layout. I'm trying to work out the best way to do the WiFi without going overboard.

My first thought was to have a standalone router with 2 U7 Pros one at each end of the apartment on separate floors but the Unifi Express 7 seems like it would suit everything just fine and it might be worth trialling just using that at first to see what the coverage is like and then adding a U7 Pro and a PoE+ switch or injector for downstairs once I've been able to do a coverage test. But I've seen some people not recommending the E7 for various reasons.

I'm getting some electrical work done in the place before moving in and I'm adding some ethernet around the place so I can basically have my pick of where to put the APs but I don't want to have to buy more than I need for a place that is realistically still quite small. If I were to get an E7 or a Dream Router 7, would I be able to set that up without an internet connection at the new place to do speed/range tests?