A lot of external drives are just internal devices with another controller and casing around. I had a 4TB I used with my laptop, and tore apart the casing and just plugged it into my desktop when I built one. Unless you start hammering the external case around, the drive will be fine.
Already been explained a few times, but GPU encoders are hardware with fixed options, with some leeway in presets and such. They are specialized to handle a set of profiles.
They use methods which work well in the specialized hardware. They do not have the memory that a software encoder can use for example to comb through a large amount of frames, but they can specialize the encoding flow and hardware to the calculations. Hardware encoded can not do everything software encoders do, nor can they be as thorough because of constraints.
Even the decoders are like that, for example my player will crash trying to hardware decode AV1 encoded with super resolution frames, frames that have a lower resolution that are supposed to be upscale by the decoder. (a feature in AV1, that hardware decoder profiles do not support, afaik.)
Completely true, but also compression can make anything bad. I’ve seen 480p better 1080p simply because the 480p was using more bitrate, where the 1080p is encoded without enough relatively speaking.