Depends. Hindsight for me, our system, 8kW, (Deye) and probably should have went with two 5kW inverters. Gives a bit of redundancy, in case one or only, has an oops. Also, the Deye 5kW is on the approved PEA list of inverters to use, as is their 10kW for 3 phase connections.
We don't need 10kW and 5kW wouldn't be enough during a week of crap weather. Or charging the EVs, which was a complete after thought, and not even considered when sizing the system for the house. Thankfully produces more than enough for both, and then some on sunny days.
Slight angled roof is preferred, or so our installer stated. When he assessed the job, said very good, not really kissing my butt, as contract was already signed. Just confirmed my design was a good one.