So I was thinking about getting the Napoleonic Wars since it's heavily discounted now. But with the existence of Holdfast: Nations at War is it really worth it to get the Napoleonic Wars now? Is the player base still exist or they moved to Holdfast? How do I check how many people still playing Napoleonic Wars?

Not sure but I remember months ago they still had lively groups of 30+ players, maybe 80 even. Haven't logged in recently though.

yeah, its the mos played dlc and i should say its more played than native in certains hours

Napoleonic wars is great, I've been playing it for years and always come back to it. There's always servers going with games that frequently have 50+ players. You can also easily find clans to play with that do scheduled line battles. And dont forget to check out the bot defense servers, they are a ton of fun.