Your yield and how many years they take to reach a useful size, will depend on the variety you plant. We see lots of biomass plantations which are harvested when still small, as they are used in boilers etc. They grow quickly initially, but I don't know if they would be as quick as other types to reach log size. We have a large variety of willows here, but the quickest growing are what I think are goat willows. They have big fat pussies in early spring, dripping nectar and pollen, so are wonderful for the bees. Crack willow ultimately grows bigger, but perhaps not so fast. There are loads of other varieties, some really fine and delicate, others sturdy and easy to grow, with a huge variety of flowers, for colour and size.
You can both coppice and pollard willows. We had lots of problems with coppicing because of voles and sheep nibbling off the buds and killing the plants, so now we mostly pollard so the new shoots are above sheep stretch, or do alternate coppice and pollard.
Another tree worth planting is the Western Balsam Poplar, which can take the wet, smells absolutely wonderful, and grows very quickly (apparently up to 60 m). We know it as Balm of Gilead.
Although they grow quickly, willows aren't the best for burning - when dry they catch quickly, but burn too fast. Still, you say you will be planting other species too. The quickest growing of the hardwoods we have found to be ash, and apart from Ash Dieback, it's sturdy and healthy.
I wish we had a nice big area for our firewood production, but we'd have to buy more land. It sounds as if you will be self sufficient in firewood before long, which is great.
We have never used any kind of weed suppression for our willows. If you plant sticks which are more like 2' than 1' tall, then you can get more in the ground to produce lots of roots, and the tops are big enough to survive the weeds. We have used protection spirals, but 5 acres worth would be prohibitively expensive, so you just have to hope your livestock and wild life don't get to them.