- SLC -> Single-Level Cell, i.e. 1 bit per cell
- MLC -> Multi-Level Cell, i.e. 2 bits per cell
- TLC -> Triple-Level Cell, i.e. 3 bits per cell
- QLC -> Quad-Level Cell, i.e. 4 bits per cell
The more bits per cell you store, the more dense and therefore cheaper your flash chips can be for a give capacity. The downside is that it is slower and less reliable since you have to be able to write and read exponentially more voltage states per cell, e.g. 2 states for SLC, 4 states for MLC, 8 states for TLC, etc.
All video codecs are lossy, meaning you will lose some quality. AV1 and H.265 are modern video codecs with the best quality to bitrate ratios, meaning you can get better quality for the same bitrate, or the same quality with a lower bitrate. The downside the these codecs is that they are very complex and computational expensive to do in software. You’ll want to make sure your GPU supports hardware encoding for the codecs you intend to record with. The reason most people will recommend AV1 over H.265 is that AV1 is royalty free. With H.265, companies have to pay a royalty to use H.265. Because of this, most companies (Netflix, YouTube, Facebook, Twitch, etc.) want to use AV1 going forward, meaning in the near future, it will probably be the dominant codec.