sorting out tire sizing: inch versus metric

[MitchFav]

project bike is a 2 stroke JOG Venice style, just screaming for retro whitewall tires with some real tire tread. Bike currently has some modern style scooter tires that have very little tread (racing look, I guess, but too modern looking and too slick in the rain). They are 90/90 - 10. Narrowed down to getting the Shinko SR550 Whitewalls, but do I get the 3.0 x10 or the 3.5 x 10? This bike has drum brakes front and rear, articulated arm fork suspension, and I suspect it could take either size, but what is the vote of the experienced people on this forum, go with the narrower 3.0 or get a little extra road contact with the 3.5's? Also, the cheap tires on the bike now are tubeless, and I am finding mixed info on the Shinko SR550's as either 1) requiring tubes, or 2) tubeless, and at least one site said tubes or tubeless. So what is it? And if tubes or tubeless, which way to go?? The current stems are shot, so I could go either way and don't really have a preference, other than tubes are easier to fix if you have a puncture (no need to seal the tire, just patch or replace the tube, if the damage to the tire is small and easy to remove)