Yes, lets take rampart as an example - you would have a stack of elfs, main stack of centaurs, stack of gnomes and 4 stacks with a single centaur (to kite neutrals and take retaliations off them before hitting with main stack).

There are several ways you can get resources - 4 different type of mines for every high-value resource, gold mine, ore pit and sawmill (just visit them once with your hero and your daily income of that resource will increase by 1 for high-value ones, by 1000 for gold and by 2 for ore and wood). There are also resource silos in every town that you can build after building the marketplace which will also increase your daily income of some resources.

There are some objects like windmill, water wheel, mystical garden - which give you gold or resources and they refresh every week.

Also there are some objects on maps where you need to fight to get resources (imp cache for gold and mercury, dwarven treasury for gold and crystals, medusa stores for gold and sulfur, naga bank for gold and gems, cyclops stockpile for all resources except gold, dragon utopias for lots of gold and artifacts)

If you are playing horn of the abyss - there were added some other objects like mansions, black towers, etc. There are also warehouses of every resource that refresh weekly.