The 2 3/4 inch will fit a 1.5 inch bulk head and the 1 3/4 fit a 1 inch bulk head (sch 40). That is a lot of flow.
I would still use the holes in the tank. This will allow you to distribute CO2 and flow through the entire tank. If you don't, it will be tough getting an even CO2 distribution with all the opposite end of the tank. I'd even think of plugging one of the 1 3/4 in the bulk head and the middle, and drill another at the far end to allow for better distribution.
I have a 180 gallon which is a peninsula. It has 6 holes (1-3/4 inch) drilled down its middle in pairs. I have 2 standpipes, 3 returns, run a sump and use a mag 18 with a needlewheel for CO2. Yes the standpipes are noticable but not too bad. The 3 returns allow for CO2 to disburse evenly. I control the return flow with valves to turn it. I only run 160 Watts of T5HO on the tank. I did try the 320 Watts I have and it was too much. Too much growth and green spot algae.
I agree that CO2 and low light is the way to go with lots of wood. It is a perfect tank for its location and will look great being able to be seen from both sides.