can you explain the difference and benefits and negatives to top and bottom bee space..
Difference is simple even for a simpleton - TBS, bee space at the top, BBS bee space at the bottom.
Neither is worse than the other although there are benefits to TBS in some circumstances and BBS in others.
Commercials seem to prefer TBS, reasons? I'll give a few but users of TBS can probably add to it.
Inspections are quicker - no need to clear bees out of the way when putting supers back on and less chance of killing the queen if she has decided to have a wander around on the top bars.
As super frames sticking to the QX is no big issue (you're not disturbing the brood area by putting a hive tool in and levering the box up away from the QX) cheaper flat plastic QX's are fine as you don't need a beespace rim to keep the QX away from the brood frame top bars.
As Dani mentioned, the original moveable frame hive (Langstroth) was TBS.
Their roofs are more like shallow trays than nationals - no crown boards needed, again, you can just prise away the roof (same for poly hives) which is one less bit of kit to lug around/lose in a wind.If you do decide to have a crown board, no ned for beespace rims on them - just a plain bit of ply needed.
In fact, as Maisie's nucs have only half beespace over the frames, the same, I don't use a crown board and the poly is flexible enough to be popped off.
BBS? you need a rim on your crown board
More care needed when putting boxes back on as bees can be crushed
I run my hives with just a beespace between the OMF and the frame bottom bars so my floors don't need a rim on them, the boxes just sit straight on the floors.
But as this thread is supposed to be discussing QX's, specifically from one supplier and the pro's and con's thereof, maybe this is too far a digression?