Thanks to tyre technology progress, all tyres for E3 & E9 are now tubeless. Initially, all cars from 3 litres upwards (in Europe, at least) came with inserted tubes. Some time later, HR were tubeless, VR kept the tubes. Tubes were used because blind faith in your tyres was a bad idea, then. In the early seventies, there were several very serious accidents at high speeds on German motorways because of tyre failure. Bad press that no one wanted.
Today's tyres have very little to do with the ones from 50 years ago. An XWX still looks like one, that's all. I've spoken to a driving school instructor (for the advanced): It drove him crazy that classic cars with modern tyres hardly ever lost grip even on the skid pad. It's the same with high-speed reliability.
Although it is nicer to use 7x14" for the 205, they also fit on any 6x14" wheel. A friend has the CN 36 mounted on the sand-cast Pedrini and likes it.
Preference of tyres usually is very individual, sometimes emotional. For the ambitious driver, today there seems to be a choice of three (in Europe). All are V-coded, required in Germany for all manual E3 of 3 litres or more, probably the same for the E9.
Michelin XWX - 205/70x14 only
Pirelli CN 36 - 205/70x14 only
Dunlop SP Sport Classic - 195/70x14 or 205/70x14
Michelin and Pirelli retain their classic profiles, the Dunlop looks more modern. All are the best there ever was, according to the people who use them. Pirelli and Dunlop perform brilliantly in heavy rain, don't know about Michelin. Dunlop is priced considerably lower than the other two.