Yeah, Breakthrough is your meat grinder mode where you have about 50 people fighting over an objective and they currently have a 'Seasons Breakthrough' playlist which is all of the new maps since the game launched. I tend to play Breakthrough if I'm levelling up weapons and just want to get 60 kills and 50 deaths...I started this yesterday, last played a year ago, what’s the go to, is it still conquest and breakthrough for popular modes, any new decent maps?
Conquest usually has an 'Exodus Conquest' playlist which is 64p conquest on a mix of 2042 maps, the new maps and also maps from Portal (so BF3 maps like Caspian Border and Noshahr Canals) - that's the mode I play the most when it's available.
Right now it's not there as they've got a 'Flashpoint Conquest' which is just for the new map - which is actually quite good and I'm really enjoying. The C, D and E points are all really nicely connected and the flow between them is great.
In terms of the new maps, Exposure was released first and I think is a brilliant map. Stranded came in season 2, kinda average to me - then Spearhead in season 3. I really like Spearhead, great map and plays well on all modes and player counts.
They've also reworked a bunch of the original maps and both Orbital and Breakaway are now brilliant, easily in my 'S' tier for maps in this game along with Exposure.