Got some slight leakers... which I hate. But also don't want to open Pandoras box by removing a plug only to find something inside which had been previously held in place by a spring but now is at engine sump bottom - scenario...
No surprises behind them Don. Just oil gallery machining access points. the ones that look like a shouldered nut should have o-rings under them. There are a couple of plugs on the back side of the oil pan that are pipe plugs. The 2 in your pic look like they have silicone sealer on them? Maybe the previous owner opted to leave off the o-rings and just used silicone sealer?
The only caution I see here is the integrity of the casting that the threads were machined in to. I've seen similar plugs and when someone tried to break free with a Johnson bar and socket the shouldered nut plug, the casting cracked. It's a good job for an impact with a light touch to break them free, then deal with the leaking issue.
According to the torque chart on pg 37 of the manual, the "oil pan passage plugs at oil pan"are a 20mm x 1.5mm to be torqued to 16.5 lbs/ft
Same deal Don. Just another machining access point for drilling the oil feed to #7 main bearing. Nothing shows in the parts manual regarding it. I suspect it also is a machined plug with an o-ring similar to the ones in the oil pan. I would treat it the same.
There's only two restrictors. One in an oil gallery and as I remember it, it's located in the upper half of the crankcase at the interface to the cylinder piston block on or about the midpoint on the back side. it restricts the flow of oil to the camshaft bearings. The second one on some of the KZ1300's there is one in the stator cover right side to restrict the flow of oil squirting on the stator rotor for cooling. Some models have the stator cooling , some don't. and as I remember it, its a .5mm orifice.