I would start with the second one because having already played the first game kinda ruined YW2 for me.
YW2 starts with the protagonist's memories being erased, which in reality is just an excuse to bring new players up to speed as you "regain" your memories (so, a recap)
The game mechanics are explained through non-optional side quests which are a real slog if you already played YW1. The first new content starts only about 8 hours in or something. Before that you basically play a very condensed version of YW1, with rehashed locations and dungeons and everything.
Keep in mind that YW1 sold pretty badly in japan because the anime started much later and the anime is what made it explode in popularity. So YW2 was made with tons of new players in mind. It's extremely newbie friendly to the point that it can be a slog to play through for those who also played YW1.
If you are gonna start with YW2 though, perhaps best to wait for the "ultimate" version that just got announced.