I've been running smartos at least since 2015 where I co-located my server. There have been times where I felt like giving up, but people like danmcd, jperkin and others always stepped in and fixed what needed to be fixed for LX to be usable and working. (Keeping java updated and running is hard, uphill battle. Thanks!)
I always ran a mixture of OS and LX zones and bcantrill's t-shirt with "Save the whales, kill your VM" made sense. I've used zones in Solaris 10 even before and they just click with me. FreeBSD's jails are nice, but far from it. And linux's cgroups are a joke. And using KVM/VMs for security containerization is just insane.
At dayjob, I've implemented multiple proxmox clusters, because we're linux shop and there's no way to "sell" smartos or tritonDC to die-hard debian colleagues, but I've managed to sell them ZFS. With personal stuff, I like my systems to take care of themselves without constant babysitting and SmartOS or OpenBSD provide just that. I don't dislike windows, I love UNIX. You could really feel those extra 20y UNIX had compared to linux.
I migrated all my stuff to proxmox for like 2 months. And then went back to SmartOS, because there was something missing ... probably elegance, sanity, simplicity or even something you'd call "hack value".
I'm running it's older cousin - N36L with 4 Drives. The CPU in that one is Athlon II Neo N36L with 12W TDP, 3.5" spinning drives are 7-10W per drive. So 40W is very reasonable.
Op should just run more services on his server, but that probably won't be 43W at idle, when the box would actually be doing something ...
There's just one slightly opaque pitfall, not all laptops have a BIOS setting where you can specify what to do on power-loss and power-resume. So the laptop "server" stays off and you need to intervene manually.
Been converting friends and colleagues to refurbished Fujitsu Futros S720 for quite some time, because RasPis are not attainable. They go for like €21 with 2G mSata SSD and 2G RAM, it's dual-core AMD SoC with up to 1.65GHz CPU frequency and 4-12W power usage.
They can be upgraded up to 1T mSata (limit) + 1T (or bigger) 2.5" SSD in mirror, 8G DDR3 SO-DIMM RAM or for example w/ 2 port GigE Realtek Network card in the mPCIe slot (reusing m-sata plastic stando-ffs). The SoC (AMD Jaguar core (AMD GX-217GA)) even have AES-NI.
For the SSD, you just need L-Shaped SATA cable and USB header to SATA power cable for peanuts from ali express.
S920 has even PCIe slot, so with riser or ribbon cable, you could hook up 4 port intel GigE network card and have 5 port firewall with pfSense, OPNsense or OpenBSD router.
I run mine with OpenWRT, because that mpcie 2-port GigE card is Realtek with lousy support in anything else than Linux.
What's uber-awesome with these boxes, they're passively cooled, so there's no noise apart some minor coil whine at boot.
EDIT: The box has mSata and mPCIe slots, but only plastic stand-offs in mSata. Ethernet card goes into mPCIe, reusing the stand-offs. Fixed that.