This ended up way more rambly than intended but hopefully will be of some help. I might clean things up a bit if I have some time later.
Drakengard
First game is a bad Dynasty Warriors clone and can be a really rough experience.
It has very repetitive gameplay and pretty much requires the use of a guide if you want to get the true ending due to things like "get to this already cleared part of the map at this specific time" if I recall correctly. Final boss is... an experience.
::: spoiler Minor mechanical spoiler for the final boss
It's a rhythm battle with no checkpoints.
:::
It has a great story (with ending E being a direct connection to Nier Gestalt/Replicant), though depending on how resistant you are to the monotony and jank, getting there might be a challenge. There are some absolutely bonkers ideas here, beyond anything you'll find in later games and that's honestly the biggest draw for this title.
Finally there's music. Oh boy, the music. It sounds like a cacophony of a madman and not in an enjoyable way. Don't expect anything like Nier OSTs.
All in all, don't feel bad about switching to/going with an LP - this text one by The Dark Id is a classic, with everything you could want (it's pretty much a play-by-play, with lots of screenshots and music, just without the tedium).
Drakengard 2
Main thing to keep in mind is that this game is kind of its' own thing and one I remember the least about.
Taro had no involvement beyond helping with a few CG cutscenes and the producer (I think?) of the first game had only a limited power over the development. Because of this writing can be a bit more generic and flat.
It's not all bad and story has some connections to the first game but it was intended to be a more streamlined experience.
Gameplay is mostly improved but has some issues, like certain bosses requiring specific weapons (you can beat them otherwise but they'll require a lot of hits).
Play it if you really want to complete the collection but it's not necessary to experience the "main" series.
Drakengard 3
This one is technically a prequel to all the other games.
Yoko Taro is back in the writer's seat for this one and the overall story is better than D2 in my opinion. I already mentioned the humor in this one - it can be a bit crude and vulgar so your enjoyment of those parts will depend on how well it clicks with you.
Story has the usual Taro flair and can be further enhanced with the DLC which expands on each of the antagonists (I don't know how easy it is to get these days).
It's not a great game from a technical perspective - it runs like garbage on the original hardware (framerate can fall to single digits at times) and can look a bit dated even compared to other games from 2013. Some of it can be improved with emulation but I'm not sure to what extent.
Gameplay is further improved (there's still a lot of jank) and way easier to fully complete so there's that. If you survived the original Nier you should be fine.
It can be an interesting experience if you like stories by Yoko Taro, just don't expect a good game (this sentiment can be extended to all pre-Nier Automata games to various extent).