Yeah basically, this all reads as a standard migration to me. I done "pretty much" the same migration a few weeks ago.
Except, instead of exchange it was Zimbra, and instead of Cloud it was from older dedicated server to a new dedicated server and instead of Windows it was Linux.
Pretty cost effective for us too as a small business everything matters - the server sets us back £35/mo which gives us an "unmanaged server" with an Xeon CPU E3-1245 V2 + 32GB RAM + 2TB of storage (well 4TB, but with soft RAID1) with a 500Mbps uplink (Which is more than this email server needs)
(Technically, it is managed - except you manage it yourself instead of the hosting provider doing it for you, the only time you contact the hosting provider is over billing or hardware failure)
I find this setup is better than cloud in my opinion simply because you keep full control of your email systems right down to how the server is configured at it's core and you are sure that no other company has access to your private company data.
It's effectively "on prem" without the cost of buying hardware or paying for the ISP connection.
In addition you are not solely relying upon a "cloud" to stay online - Yes Microsoft we all know about those outages.
But yup, it's my preferred way and has been working well since 2013 - in that time we've had one outage caused by the DC which lasted a grand total of 5 minutes.
(Apparently one of their network switches died during a firmware update)
We've had two HDD's die in that time (Separate incidents, different servers) - At the time they were using Toshiba/Seagate/WD drives - I had a Toshiba and a Seagate drive replaced with HGST and our current email server came with HGST as well. Both happily replaced with no extra charges by the DC.
So overall I'm happy with this setup :-).