Dave, usually the cables do not require oiling unless they are sadly neglected or on their last legs. A couple of other things to check would be to make sure the throttle tension screw (under the grip) isn't cranked down real tight and also the throttle grip tube might need to be cleaned/lubed as well as the mechanism. Since this model probably has a single upper cable going into a splitter with two cables coming out for the carbs this splitter assembly could also be crudded up inside as well. The cables are joined together with a plastic "piston" or coupler that if it gets grungy could contribute to a harder than normal throttle pull. If everything is cleaned and lubed and the throttle is still too heavy for you you can always replace the return springs on the carbs with lighter ones, I have read of folks doing that .
As far as oil goes probably for anything above freezing 20w50 would be fine, definitely 20w50 in the summertime. The gearboxes often prefer a heavy weight synthetic, I use 80w140 in all of mine and they seem to shift better than with the 75w90.
You commented on the riding position. I think all of the R65LS models destined for Europe had the low bars (Euro-bars) but those intended for the US specified the taller "touring" bars. If you wanted a more upright seating position you might be able to find somebody to swap you, or come up with a set of the "high bars". This would likely necessitate changing out the clutch cable, upper throttle cable, upper choke cable, and maybe a brake hose as well.
You look to have a very nice machine and it should serve you well, and welcome to the forum.