Regarding the placement - it really depends on what sous vide racks you'll be using (but I find the corner best for mine) - where it is in the vessel really doesn't impact the PC's ability to circulate the water, so why not put it in the corner, out of the way?
You may want to investigate the type of plastic the lid is made out of. One advantage of the Cambro is that the lid is also polycarbonate and it locks - producing a seal (i.e. no evaporation). But, being polycarbonate, we know it will stand up to the same temperatures of the bin. A softer plastic/polymer may not be viable with some of these temperatures. Indeed - I wouldn't leave it unattended...be a horrible thing to come back and find your PC actually IN the bath, shorting out.
That's the thing - many of the cooks you do for things like ribs, short rib or brisket are prolonged cooks - some up to 72 hours. You really need to be able to rely on the stability of your vessel for the duration of that cook.
(reminder, getting a UPS - interruptible power supply - for long cooks is also a very good idea, as the PC will NOT resume a cook if it loses power as a safety feature).
btw...the Cambro has handles...the entire lip around the edge. I normally fill it in my kitchen, then walk it to the back room to get the cook underway.