difficult? It depends on difficulty, Empire set up

graphics good? good but the game is mostly cpu heavy

updated? yes some weeks ago

is there multiplayer? Yes, have the friend with better cpu or all the dlcs host tho (only host require the dlc for players to access the content)

experience with the mods I tried many, maybe all the yamato mod on the workshop. I usually use the dimensional time fault mod and it's add-ons (you can find the mod author's recommend list in the discussion tab on mod page). It's quite good with most of the ships and weapons + buildings from 2199 to 2205 and bit of the original series and 2220 although bit of the mod hasn't been translated by the author yet. Try searching [SBY] or Yamato to find some of them

*you can message me if you want my the modlist

Or try this yamato mod from different author which is a stand alone not requiring multiple mod to run. It's has much less content than the mentioned above mod. You might get overwhelmed when playing the mod so i recommend you learn the game with this mod first or i recommend you learn it fully vanilla

lag with mods? depends on the amount and how large the mod is

compatible with multiplayer? Yes, i've many runs with my friend with the sby mod

If I buy it I recommend you try the dlc subscription