I can answer one question - you need the water to get to the bottom one way or the other. You can do that two ways - either cut a hole to plumb directly into the bottom (you'd need to use a gasket or bulkhead to stop the barrel from leaking around the pipe) OR you can put the pipe up over the edge and down into the bottom. Either way works fine. The second way will avoid the leaking issue, but it does leave you with some plumbing you need to conceal. Bring it from the back, up close to the side, over the edge and back down and you'd barely see it once the plants start growing.