Which Oil (also filter and 'wet clutch' question)?

I know it's a bit like which toothpaste or which bread but I need advice about oil for the ZXR750J. Value for money is good, protection (obviously) and easily available. It's just a weekend warrior toy for fun in the twisties, I'm not revving the ring out of it. Will probably change every 4000km or so.
Also does anyone have a Ryco part number for the oil filter? I've checked the website but it must only look up cars it keeps thinking I mean Kia
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Also Is it good or bad to use that Nulon Oil System Flush stuff on bikes? I used to use it on the rally car to clean out the system before putting pretty new oil in.
Is the clutch a 'wet clutch' in this bike, and if so is it 'wet' by the engine oil? I don't know that much about bike clutches, but I've heard the term 'wet clutch' around, surely oil anywhere near the clutch plate faces would make it slip?
Maybe there's a couple of different topics here but I've stuck it all in the title, who can help?
Also does anyone have a Ryco part number for the oil filter? I've checked the website but it must only look up cars it keeps thinking I mean Kia

Also Is it good or bad to use that Nulon Oil System Flush stuff on bikes? I used to use it on the rally car to clean out the system before putting pretty new oil in.
Is the clutch a 'wet clutch' in this bike, and if so is it 'wet' by the engine oil? I don't know that much about bike clutches, but I've heard the term 'wet clutch' around, surely oil anywhere near the clutch plate faces would make it slip?
Maybe there's a couple of different topics here but I've stuck it all in the title, who can help?