Going into The Legend of Heroes: Trails of Cold Steel II, I'd never played the original game. So my background information on the title was limited to the official game description and what I could piece together from the opening sequence of the game's story. Which is probably not the best way to pick up a series, and definitely not with Trails of Cold Steel which has a ton of worldbuilding and lore behind it.
However, I was able to peace together enough of the plot to follow through with the rest of the game. Honestly, outside of its own lore, the game is a pretty standard JRPG that focuses on the bonds of friendship.
The combat is typical turn-based JRPG fare, however that's not much of a focus of the series, which is more of a playable anime than a video game. So if you pick this Trails of Cold Steel II up for the gameplay, you'll probably be pretty disappointed. And because it's a story-based JRPG, for better or worse, there's really no reason to pick up the second game if you haven't played the first since it is a direct sequel that picks up immediately after the first left off.
The PS4 version of Trails of Cold Steel II is a pretty straightforward port of the game from the PS3, with a few extras like additional voice recordings, access to the Japanese voice track, and a higher resolution. However, it's still, at heart, a game from the PS3/Vita era and it looks like it.
Bottom line, if you picked up the PS4 version of the first game and played it through the end, you'll definitely want to pick up Trails of Cold Steel II. But if you haven't played the first, there really isn't much to be had from picking up the series in media res.
The story of the series has been highly praised, though I personally find it a bit tired. So this one really comes down to your own personal investment in the characters and their stories.