I do this since last 2 year in my engine but using custom templated compile time data structures to generate GPU structures with correct alignment and special validations. I get nice typed interop between CPU and GPU for data structs and compile time validations. I have not seen what boost.PFR does.

Maybe they worked like puffer fish🤔

Is it one of '|' '||' or '&' '&&'?

I think it is. I am ignoring the self described expert from the start and at this point I even blocked. It was so annoying and reading the comments was infuriating.

I think the main reason for using CPU simd over GPU is latency when it comes to audio programming. I have no experience in audio programming.