Around high water (especially about an hour after) the tide will go slack just as it does at low water, and the flood tide is generally weaker than the ebb so with good timing you should be able to avoid the strongest tidal flows, half tide is the worst time to run against tides as they are strongest.
Running against the tide you will have more steering control than some of the things you see bobbing sideways towards the yarmouth bridges with the tide taking them as they try to keep the speed down, most boats should be able to push against the tide just won't get anywhere fast, and if headroom is low you are better going under a bridge against the tide as you can stop far quicker by dropping the throttle, the other way round (with the tide up your bum) you just career under a bit slower instead of stopping, might use less fuel but can use more toilet roll.....
Remember the bure runs out for about an hour longer than the yare, I assume the opposite is true at high water.