I'm scrolling horizontally in Xevious. I use two lots of linked sprites.

Each frame (when scrolling) worst case is that you just need to reposition 2 sprites, unlink one and link another. Although the logic is a bit tricky it's still only 4 SCB accesses, which is the key here. I keep track of the left-most sprite in a variable to make things a bit quicker. I also have coded two distinct cases; scrolling that does not require the sprites to change (7/8), and scrolling that does (1/8) in my case (I'm using 50% scaled sprites on the background).

Worst case is when resetting the scroll position to an arbitrary value. Instead of trying to optimise the SCB accesses, I simply unlink and re-link/re-position everything. It's only done very infrequently, and not done during active gameplay.

Also I can confirm that any sprite with height > 0 will be placed in the sprite buffer, regardless of position (on MAME at least, but that is what the MVSTECH doc says too). Not ideal, but that's how it works.