Henry Cavill was quite clearly chosen because he is a handsome gentleman
He can be handsome twice as much he is, does not matter. Dude has zero charisma. Good for modeling and playing hot dudes in soap operas and romantic comedies, terrible choice for any sort of serious role. Couldnt stand him as Superman, nothing changed in the mean time. Mads even tho he is a bit old would be far better choice. But he would suffocate those poor female leads they are trying to put into spotlight. Thats why they picked possibly the worst famous actor they could find nowadays, even Robert Pattinson has greater range of acting. Not to mention he would be better Geralt than Cavill. Basically anyone would make better job at it, even short actors like Tom Cruise or terribly old like Eastwood. This is a set up to make Geralt look terrible.
Yeah, that was a bit weird since wider audience doesn't know shit about anyone but Witcher himself. Though if they want to show in season one how Yennefer became a sorceress that will be quite cool I think. And in the novels the most important character was actually Ciri, not Geralt. He was the main character of original short stories ofc. All in all I liked it.
Only reason why is this being made into a show is Witcher 3, not 2 or even first game. Certainly not because of some books written by Polish author. In that game Geralt is the boss, everything revolves around him. While this may be more book accurate, very few eagerly awaiting this Netflix show give rats ass about the books.