Ours free range, are noisy and good guard dogs, we never shut them in. They're usually up and about first thing, big sleep during the day, up again in the evening until late. We've never had one of them taken or injured. They eat lots of grass, love iceberg lettuce (just leave a half one out every few weeks) and ours eat mixed grain (same as chooks) and we also give them flaked maize (aka cooked maize) which looks like big cornflakes. They're not overweight. I've seen them eat the windfall apples and they eat uncooked potatoes I believe although ours never have, they have quite a serrated beak.
We have a large pond and they tend to rule it over the ducks. If you don't have, then do get them something they can have a swim in and that you don't have to change that water too often, then just get a bucket filled to the brim every day (so easy to change) and leave it out for dousing and drinking, that would work.
The ganders become very aggressive from late Feb to late May but will change overnight when their ladies start to sit. The rest of the year they back off if I get too near them. If you have to catch them they are placid enough unless it's springtime in which case I wouldn't try and catch them. In spring they'll go for the kids before you (at least mine do) so my kids take a very wide berth.
Sexing - males tend to be bigger, thicker legs, bigger head, likely to be the one(s) awake while the others sleep, act a bit more forwards in the group.
I love geese, they are intelligent, graceful, big pests and very economical to keep but they are very loud so if you have neighbours ... our girls sit in April / May time but they are useless mums, so if you do that I would incubate or take the young away (sounds heartless but they will accept them when a bit older and past the vulnerable stage). Goose eggs are great for custards, big sponge cakes, meringues and lemon curd like your granny used to make. Enjoy your big pests.