... I find it so hard to position things in Bryce, ...
OK, some pointers in moving stuff into position in Byrce.
Sorry if I'm telling you stuff you already know, but if so, let's hope it can help other people.
1; If you have a large, complex scene the components will be slow to respond to movement and jump around, so make sure you have the wireframe view set to 'Default Wireframe'. This option is down at the bottom right of the viewport and is identified by it's little icon that looks like a wireframe cube. Click on that and from the top section of three, make sure that the Default Wireframe has a tick against it.
2; There are several ways to move things around in Bryce and selecting a component and dragging it around with the cursor is the least efficient way. So select the component you wish to move and then in the "Edit" tab on the top row of icons, use the icon that looks like a cube with arrow heads on the stalks that stick out of it.
Now this can be a bit confusing because your camera view doesn't necessarily match with the natural North, South, East and West orientation of this movement icon. One way around this is when you start to build your scene, go to Top View and make sure your camera is at the bottom of the default grid, pointing North. Then your movement and re-sizing tools will a bit more sense. Otherwise hope you get used to sometimes having to move the movement icon arrow one way to make your component move in the opposite direction.
So if you've set up the scene as suggested above, to move your component North you put the cursor on the Movement icon at the point where the lower left arrow stick out (the cube will slowly throb and you should see an 'X' to indicate the X axis is selected), now slowly move the mouse or trackpad to either push the component North or pull it South. If you wish to move it in smaller increments, press the Alt/Option key at the same time. This same process can be used to move a component (or group) East, West and Up and Down but choosing the corresponding arrow head on the movement icon.
You can also move stuff by selecting it using the arrow keys on your keyboard. Again, if you wish move things in smaller increments, you can use the arrow keys in conjunction with the Alt/Option key.
You can also move stuff by clicking the little A in the components sub menu to access the Attributes and type an exact position in the matrix grid.
3; Moving stuff into position is much easier in Top View and once it's close enough, for more exact positioning, zoom in to the area.
Zooming into the area is easy in Top view as Bryce will automatically center the selected component in the viewport. The zoom button is found at the bottom right and is a magnifying glass with a plus (+) symbol. there is also a zoom out button with a Negative (-) symbol and a move around button with a picture of a hand which allows you to scroll around the view. Using these buttons will not affect the view when you go back to Camera or Director view. Zooming in has another advantage as there is less geometry in the viewport, moving items should speed up.
4: Now your item is in position it may not be at the correct height.
If it needs to sit on the floor and is at present floating in the air, just select the item you need to position and in the item's sub menu, click the bottom icon (an arrow pointing downwards). This will drop the item down to either the floor or the surface of any object it first comes into contact with.
If your object is below the ground and it needs lifting up, Bryce will put a little upwards pointing arrow in the sub menu instead of the downward pointing one. Clicking it, will bring your object up to the ground level.
If there is no little arrow in the selected item's sub menu, it is already at ground level.
If you're altering the height of an object and it doesn't need to sit on anything (a plane in the air for instance), use either Left, Right, Front or Back view to see an overview of your scene and using the movement instructions above only selecting the Y axis movement arrow head on the movement icon and remember that pressing the Alt-Option key at the same time will move your object in smaller increments for more exact positioning.
Hope this makes sense (it's early here) and that some of it helps.