There are tubeless ready (TLR) tyres and UST tyres and the same for rims. Some TLR's are better than others. some rims work better than other's too, ie inflate easily with a standard pump and hold the tyre on the rim better. UST rims and tyres in combination provide the best rim /tyre seal thanks to the bead groove design. Riding style also plays a big roll, ie how hard you make teh tyre work in corners etc. My experience is that stiffer sidewalls and higher pressures are needed to keep non UST tyres on non UST rims. That said, some TLR tyres are simply better at rim retention and these are generally the heavier stiffer sidewall tyres like a WTB Bronson and Hans Dampf. In the AM tyre arena, there are some wannabe tyres like Spaz Purgatory which have thinnish sidewalls and almost too much grip for my converted rims - ie the grip on the ground exceeds the rim bead grip and they burp. They also bleed sealant through the sidewalls. Ultralight versions of the Nobby Nic are next to useless on my DT E540 rims rims. Basically, if you want security and grip on a TLR set up, you are usually going to need to go heavier and stronger, depending on the rim tyre combo, and your riding style. Its not all bad though because a UST rim and tyre combo is also not that light as the tyres are stronger and thicker than some TLR tyres. As far as inflation is concerned, if you have the right rim strip/tyre combo on a TLR set up, it should pump up as easily as a UST rim/tyre combo. the big factor seems to be how tightly the uninflated tyre seats in the middle of the rim before inflation. If thats tightish the butyl beads seem to trap the air well and they pop into the groove easily. in fact my TLR DT's pump up easier than XT UST rims with some UST tyres... Experimentation is the name of the game.
