There are simple testers like this. It’s rather overpriced for what it is, but it would be trivial to make one yourself. That will only do a continuity check though. If you want to know what the current or speed ratings are, you will need to read the chip in the cable.
A dedicated GPU will mean reduced battery life. If you are only going to edit video at your desk, I would suggest getting a laptop with a thunderbolt 3 or USB 4 port and an external GPU. Make sure the port provides 4 PCIe lanes, not all of them do.
Timeshift works best if you use BTRFS for your root partition because snapshots can be taken instantly. I have mine setup to automatically take a snapshot every day.
The MOSFETs are in series, but in opposite polarities. Two MOSFETs are needed to block current in both directions.
The DW01 uses the voltage drop across the MOSFETS to measure the current. The overcurrent threshold voltage is fixed at 150mV. Using a larger MOSFET that has a lower RDS(on) will increase the current limit.
The drains in the 8205 MOSFET are connected together internally. In a DW01 circuit, they are not connected to anything else.
One MOSFET stops the battery from charging and the other stops it from discharging.
For something that’s not switching at a high frequency, slow rise and fall times are fine as long as you are staying within the safe operating area of your MOSFET. A 10K gate resistor could certainly work, but it will depend on your MOSFET and load.
Power consumption is the main issue. If it’s an old, power hungry desktop and you live somewhere with expensive electricity, it can be quite costly to run. If you have an energy efficient desktop or have cheap power then it will be fine. Just make sure it has a good quality power supply if it’s going to run 24/7.
The hard drive should be connected by SATA or eSATA when making the image. Connecting over USB is just asking for more trouble when the drive is not working correctly.
I’ve gotten both of my thinkpads used, so none of that money went to Lenovo or Microsoft. The laptops that come with Linux are expensive and are rarely available used.