OP you can run the equivalent to a 35 metric or standard tire with a 2-2.5" lift in the front. You can have rub or you can be fine, it depends on wheel size, tire width, tire thread, caster numbers, suspension components etc.
I can't tell you anything about 20" wheels cause i don't run 20" wheels. But there are some people that have tried various combinations and know what works close to a science. Lots of people run 34's to avoid any kind of rubbing issue, and depending on the gearing you have makes it better to run something a tad smaller and lighter. If you have the 6 speed trans with 3.21's 35's are not going to be a good idea.
From there is a matter of preference how much gap would you like to see between the tire and the fender. Some like a big gap between the tire and the fender, for some others a little stuffed looks is lovely, some others will like to slam the vehicle to the ground, there is no right or wrong here, just go with that you like to see.
You can keep the 33 height but go wider. If you go with an aggressive MT and wide 33's, the tire will appear a little bigger than what it is so it's a trick that works if you like the size. You can go 34 or 35's tops without having to do much to accomodate the size, but again you have to pay attention to wheel width and tire size, lift amount and alignment. We have been blessed with huge fender wells that make possible to run bigger than factory tires, but remember the bigger you go the more money you need to make them work.
Have fun.