The easy answer is that you can do anything at any time, as long as you are within the limits of traction and ground clearance. If you need more lean angle and aren't dragging hard parts, then lean the bike more. If you want more throttle and you aren't spinning, then give it more gas. If you need more brakes and you aren't locking or tucking the front, then apply more brakes. You can do anything, either while vertical or leaned over, as long as you aren't dragging hard parts or exceeding the available traction.
The biggest mental hurdle for newer riders is this idea that you can only do 1 thing at a time (brake, gas, or lean). The fact is that you can do any combination of them at any time. The only limiting factors are ground clearance and traction. But even exceeding the limits of traction isn't a big deal, it just takes a good feel and throttle/brake control to be able to stay comfortable with it.
I posted this picture in another thread, but this is an example of doing 2 things at once. All things being equal, if you aren't spinning the rear, then you can go faster. That fact holds true no matter who you are, what bike you are riding, which track you are on, so on and so forth. If you haven't exceeded the limits of traction, then you can go faster. The trick is to be able to ride right on the limits of traction, possibly even a few % over the limit of traction (as in this picture with the rear spinning and leaving rubber behind), to ensure you are going as fast as the circumstances will allow at that moment.