What are the better options?

Pis have great software support so for GPIO experimentation it's so useful.

If you have the lid closed, you’re looking at 3 to 15 watts to have a laptop running in the background doing some basic server shit.

Not all laptops make effective use of power with the lid closed, sadly. Not saying this as a correction, but for others to know that they need to make sure these settings are available in the bios of the system they are buying.

Laptops are not generally designed to run like that with a closed lid. Heat dissipation is designed around the idea the laptop is open and some of it is through the keyboard surface. The lid closed would change that.

Systems can of course be setup to power off the display but for server/service uses open laptops may not be efficient space wise.

Having said that if the scenario is low power use the heat dissipation may not be a major issue. But if there is an unremovable battery i'd still be concerned about heat dissipation with the lid closed and even just the battery itself regardless of heat dissipiation.

Not quite. Unless the system has pretty advanced power management and is using very recent technology with high density, it's unlikely that an x64 chipset will use less power than a comparably powered arm64 chipset. Not just the processor, but the smaller board is actually a power saver and allows it to generate less heat meaning both less power wasted and dissipated as heat as well as less power needed for fans to properly dissipate the heat. I've never seen a laptop use 3W at idle when considering the whole device, maybe just the CPU, but not if you include the rest of the components like RAM and disks and power supply. And especially true in a laptop that is old enough that it's being recycled. Heck, the power supply and charger alone might be using 3W at idle with full battery.

With a raspberry pi 4, the typical power usage for the 2GB RAM model is 5W under load for the whole device and about half that for idle. Add a couple of watts for the extra memory and wider bus on the 8GB model and other things can add to that, but that's mostly accurate. The pi 5 is a little more and the 3 is a little less. Of course, the efficiency of the laptop at full load might end up being better than a comparable number of raspberry pis it would take to do the same amount if work, but comparing a single pi or any other reputable arm-based, single board computer to a single laptop at idle is always going to be that way.

Battery charging circuits don't operate continuously when the device is charged. Pi also still needs a PSU, typically a phone charger, and for a server application would need an SSD or HDD in most cases. SD cards have lower performance, write endurance, and capacity after all. A single raspberry pi couldn't match even a somewhat old laptop in performance. In terms of actual efficiency (performance per watt) Pis don't do that well as they are using cheap processors made using old core designs and even older process nodes. Even the latest Pi 5 uses a 16nm process node with a core design from 2018. A 10 year old laptop might have 14nm process node which would be better. This means that a laptop would have more performance, so even if it had more power consumption at peak it could still end up with significantly better performance per watt, and that extra performance allows it to idle more often as it spends less time processing requests.

Of course the ultimate in performance per watt is always going to be a modern high power server or an Apple Silicon device. Mini PCs can also do well for home use, and are much lower power so better suited to less demanding usage, and have the best performance per watt for consumer devices. The M4 Mac Mini for example is pretty much best in class in performance per watt, and low power consumption at the same time.

Battery circuits come on enough to be a load that needs to be considered and will show up if you measure load on the device vs load consumed by the components connected to the power supply. In terms of low power devices, it is significant, though not the primary concern. But compared to the pi PSU, the charger not to mention the battery and internal PSU of a laptop, consume way more power and produce way more heat.

All of the rest assumes needing always on, heavy load processing which isn't what the post I replied to was talking about. I was specifically replying to idle power load. And in my case, even with a bunch of self hosted applications, most of the time my servers are idling. If I was running a virtualization farm or something that was always under heavy load, then yes, as I mentioned, a single board server isn't ideal.

As for disks, I don't use SSDs on my pis except one that actually does a lot of local data processing. Everything else runs in memory and stores persistent data on my NAS, including logging. Virtual memory/swap is disabled on all and things that need temporary storage/cache of small amounts of data is cached on RAM disks where applications can't be configured to not use disk caching. The only need for the SD card is for boot and some minimal IO needed for local OS operation. I have a Raspberry Pi 3 B i got about 8 or 9 years or so ago with the same SD card in it.

They aren't what I use as a database server, obviously, but they are extremely low power compared to what an old laptop would need and work great for things like pihole, and other network applications as well as being a part if my home kubernetes cluster and run the majority of the cluster's processes on demand.