I've tested the multimode transmitters and got somewhere around 15.4dB when testing with a 1m 62.5/125 fiber jumper at 1300nm. Singlemode I don't remember off-hand but I believe it was about the same.
Yes, the singlemode appliques have FC connectors. If you are attaching 2 singlemode appliques together, no attenuator is needed. I've had some connected in a lab scenario with only 2 meter jumper cables.
However, we also have a situation here where we have a short singlemode run (~500m) where we go: