Size right for your setup and risk tolerance. Just know every outage can come with data loss. Most do not, but it is not a guarantee.

Your pi is idling at 4w? That seems quite high. Does it have a nvme drive attached or something?

UPS systems are generally configured for 90 minutes of operation, depending on the criticality of the system they’re connected to. The best ones are programable and will actually send graceful shutdown signals (when configured to do so) to your server cluster to prevent data loss that occurs during system blackouts. You can emulate this behavior on your laptop with a script that checks battery% every 10-15 minutes, sending a shutdown signal if it falls below a treshhold you set.

You’re mistaken. Laptop cells do not behave in this way or use LiPo chemistries. They’re Lion chems and behave entirely different.

Some won’t boot without a detectable battery cell. Depends entirely on the laptop in question what the best course of action is. Most newer bios handle charge profiles automatically and will prevent ac related damage but it’s all dependant on how they were designed/made.

Laptops run on “burst” computing profiles in a lot of engineering situations, occasionally this applies to both the thermal design (runaway heatsoak if used at full tilt) but also battery design. I’ve seen several machines that will dip into their battery in addition to the charger to boost performance and dump wattage into the chips beyond what would be available from the adapter alone. I don’t necessarily think it’s good design, but modern battery chems don’t really give a shit about up/down momentary charge cycles. Also the Chem they’re using is not LiPo based as that chemistry while allowing for significant amperage to be drawn, is not stable enough for a laptop that is generally expected not to ignite.

It depends on the drive and the type of drive, but generally they actually start to suffer bit rot after 6-12 months if they’re left without power at all. DVDs also suffer from bit-rot on short time scales, especially if stored improperly. Also migrating data or having a copy of it on a hard drive is easy, copying DVDs is legally gray, difficult, and they really only make sense as a delivery vehicle for the file to a drive or tape (if you prefer something genuinely long-term storage ready).

Something that people are missing with the whole physical media situation is that it being physical does not preclude it from internet connected DRM, server requirements, etc. It just so happens that around the turn of this century DVDs came along and lacked sophisticated/connected DRM implementations, but it is not inherent to their physical nature. Physical media also decays. DVDs generally have around 20-25 years before bitrot starts to set in. I love the concept, but you’re better served by a hard drive than a DVD.

It’s likely done in an automated way by the same equipment that tests the hardware, so costs are probably more along the lines of a few fractions of a penny, and imo shipping any device without an os at all is a bit silly as they could very likely end up in the hands of someone without the capability or equipment to image them.