@Russ .. Could someone please explain what the ' conditional move ' option is , how it is used & any other insights & nuances that may illuminate my foggy mind .
It is a means of setting your reply to your opponent's expected move on condition
they play that move. On the site from the gameboard screen press the "conditional move" and the current position is shown. Play your opponent's expected move and record your reply and save. If your opponent makes that move your prepared reply will be made automatically. On the android app it is similar except you press the diverging arrows symbol at the top of the game board screen.
Quick mode allows you to set your opponents expected move from the current position and reply, but allows you to set replies for multiple potential moves from the current position, for example if he can take your knight with either a bishop, rook or pawn you can set a reply for each of those possibilities. If you want to follow any line further in you need Deep mode and you can programme in a sequence, saving after each of your moves, all the way to mate. It will only fail where your opponent does not make the expected move. Once the moves are prepared you can check them on the queued moves board.
On this site your opponent cannot see your intended move until it has been played so you are not giving away any plans before the fact which has always been the main objection to conditional moves. If you are the sort of player that thinks about moves quite deeply then you can argue you lose some thinking time by replying straight away rather than holding on to the position for a couple of days and going a bit deeper. On the other hand using them speeds the game along by making moves when you are off site, in bed or down the pub or playing an opponent who is on the other side of the world giving them a chance to get an extra move in while they are on line.