I have been using it more heavily since turning off the pointer grab, so I have triple checked. I turned mouse grab back on and the cursor immediately slowed down and became big on some motions, mostly rapid ones, but sometimes slow ones. Turning it back off makes the cursor move smoothly and consistently again. When small, the cursor is completely white. When big, it has a black interior.
Having ‘show remote cursor’ and ‘mouse grab’ both on has one big cursor, apparently the local one, and one small one, the remote one, which never enlarges. It seems to happen when the remote cursor falls behind the local cursor. With ‘mouse grab’ turned off, when the local and remote cursors separate, the local cursor remains small, unlike with ‘mouse grab’ on.