Get a 2.1 bar radiator cap (like the CV4) and you will puke anywhere from zero to minimal coolant. Even when I go tractoring around in 1st/2nd gear stuff through the woods with minimal airflow through the radiators for many minutes on end in hot summer weather, I lose no coolant. Stock was 1.1 and would puke all kinds of coolant into the bottle; got a Tusk 1.6 and it was better but not 100% (and it's now on my YZ250); 2.1 is the ticket for the WR, especially if you don't run a fan or higher flow water pump or something. Triple semi-colon use there, btw.
+1 on this.
Fancy coolants may have much higher boiling points than water + glycol, but they are poorer conductors of heat. As a result, your engine runs hotter when using them.
A 2.1 bar rad cap allows the water+ glycol to get hotter before it boils over. The engine runs as cool as it can because the water and glycol are better conductors of heat and if it does get too hot, it will steam a bit. With the fancy coolants, you get no steam, but the engine is running incredibly hot.
My engine has only ever steamed a tiny bit with the 2.1 bar cap. Both times were on super slow slogs with lots of clutch work. Even then it only steamed a tiny bit. I'm sure a fan would have probably prevented the steaming, but its not worth the hassle and weight to run one.
I check my coolant about every 5th ride. It never takes more than a tiny bit to top it up and I'm probably overfilling the rad when I do. I see no reason to run a catch bottle.
My WR overheated regularly with the stock 1.1 cap. It was a bit of a joke how often and long it would steam. Whenever we stopped the catch bottle would be bubbling.