I have cleared a lot of land like what you described. What I have found is that on trees up to 8" I can fairly easily knock them over with my TN65 which is a 52 horse tractor. If the tree doesn't want to go over I start digging witht he bucket at the base into the roots. It will then push over easier. Any tree that is too big to get pushed over will need an excavator to dig it out or you will want to leave it stand and farm around it. If you cut it off and leave the stump you will most likely find it with something you shouldn't. As for the small brush, I brush chopped it all down then plow it under with a 3 bottom, 14 inch plow. It will pull up the roots and the first two years are a hassle but what I do is as I plow, disc and cultimulch I keep stopping and picking up the larger root stumps. I plant the field into corn the first couple years as it allows me to keep working the ground and kill off the weeds and such with a couple years of good weed control on the corn ground. Around the third year almost all the roots are gone and the ground is smoothed out, weed free and the soil is in better shape as I do soil tests each year the first few years on any new field to build it up properly (then every other year after that). The third year I will plant it into a small grain unless I feel the need to plant it to hay right away. Planting it to a small grain allows me to use a different weed spray on it that helps eliminate any weeds that the spray program I use on corn ground may not have been as effective with. There isn't usually too much weed issue but it does help. Then after harvest I notill in the hay seed into the grain stubble unless there is an issue with the field where it needed to be plowed again.
It is a very fun project reclaiming farm ground. I have reclaimed around 75 acres over the last 10 years using my TN65 for most of it and a John Deere 450G dozer for a month to clear the heavily overgrown vineyards. One month with that dozer cleared a lot of ground and I only used it after work and on the weekends. I just dropped the blade at the end of the row and pushed all the posts, vines and wire in to the middle of the field and made huge piles and set them all on fire. The wires were the biggest challenge because of the tracks but its just a case where you have to pay attention. I could have done it all with my tractor but the dozer was a friends and didn't cost me a dime to use. I have since cleared 3 acres of vineyard with my tractor and that was more labor intensive as I had to pull the wire first, pop each post seperately with the loader then get everything off the ground so I can brush chop the vines before plowing. Its in its second year of corn now and the field is smoothing out nicely.
If you have a lot of large trees though I would look at renting a large excavator for a day or two as they can remove the biggest trees quickly and then you can take your time on the rest of the ground with your own equipment. I am almost done clearing land now though and only have to clear up the edges on a few of my existing fields to push back the woods that have been encroaching for a lot of years. Once their done this spring I will be sad as I will not have anymore to reclaim

I really do love it