OK here's two charts courtesy of sycamore
Looking at the first one, it shows turn perf for aircraft at three different weights.
Look at the innermost of the bold black lines. It starts at just under 200km/h at 0 turn rate - thats the 1'g' stall speed. As you go 'up' the page (and so cross lines of 'g' or turn rate) it curves to the right, showing an increase in speed - that's the stall speed going up as the 'g' increases. That's why the first curve, that bends up and right, is marked 'lift limit'.
Follow that curve all the way up (past the branch at 13.5 deg/sec, which we'll come back to) and you get to a fairly right angled corner, at 7'g', 24 deg/sec, 400m radius. Thats the point where our lift limited 'g' runs into a structural 7'g' limit. So past this point we can't continue to pull to the lift limit - now we follow a line of constant 'g', until we get to 15 deg/sec and 910kph - now we've hit the max speed, and can't go any faster.
that line just followed is the absolute maximum turn performance at 4,400kg - so it represents the maximum instantaneous turn rate.
The reason it is "instantaneous" is that it cannot be achieved for more than a split second.
If we now start again, but this time stop at the branch ignored earlier, at 13.5 deg/sec, and follow the line marked 'sustained turn rate' we are now seeing that the turn rate we can achieve is much lower - at 500kph, for example, the max instantaneous rate is about 22 deg/sec, but the max sustained is about 12 deg/sec. that's because the aircraft doen't have the power to overcome the huge induced drag at 5.5'g', but does have the oomph for about 3'g'. At the max speed end everything collapses to a speed limit of about 700kph - the aircraft hasnt got the power to reach its max speed limit in level flight.
The second chart tells much the same story, except its a very high drag index, so lots of stores. So the aircraft, this time, can't get to 700kph - this time it maxes out at about 650kph.
Does that help at all?