Hey Jared! Good to see you here bro.
Okay, the Nighthawk CM1200 has "DOCSIS 3.1" which will support up to a 2Gbps connection. Of course, this depends on your internet connection and if you need this. I would get the 1Gbps version personally. Now, for the speeds that are stated, This is on a Wired connection, and wireless will, in most cases, be much slower. There is what is called "MIMO" which had dedicated paths for wireless that can make individual devices to work faster, but there are only so many lanes.
As for Link Aggregation, the ONLY reason you would need this is if you had a SECOND internet link coming into your house. You would pay twice as much for internet. Doing this would theoretically double your connection speed by splitting packets between each of the links, but IMO, it's not worth it unless you are running a server that needs a dedicated gigabit network.
Let me put it this way. I have a fiber connection in my house and have internet speeds that are 1000/1000 Gbps up/down. I have NEVER even come close to saturating this network with the exception of large files from really good servers, which is rare. Normal every day work (yes, I work from home and have for quite a while now) with everyone else (I have two houses on my internet with 4+ people always watching Netflix, YouTube and the like, and I have never noticed anything slowing me down.
My network (LAN) is only a gigabit network, so when I am downloading those large files, and I"m actually able to download at a gigabit, I'm saturating the network. I do have plans of future proofing by installing all 10Gbps on my network, but that is a ways off still.
Suffice it to say, even with a 400Mbps link (about 50 MBps), unless you are downloading very large files all the time, I can bet that you will never see any indication that anyone is on the network. With normal use, we are pulling about 200Mbps on my network at the max.
All of that to say, unless you are wanting redundancy, link aggregation is not worth it. Just get a good modem, make sure that all copper from the modem to the pole is brand new and make sure it is at least RG6. Anything smaller than that will reduce your speeds.
Hope that massive post answered your question.