Does the mount swap work on all four systems?

Yes. Each lens ships with one mount, and Sirui sells E, L, RF and Z mounts you change yourself with a simple tool. Swapping takes a few minutes and keeps the same lens across bodies.

Is T1.4 usable wide open?

It is usable, and that is the point of the set for low light. Expect the corners to be softer and contrast lower at T1.4 than at T2.8 or T4, so stop down when sharpness across the frame matters.

Do the three lenses match each other?

Sirui designed them as a set: same 80mm barrel diameter, same gear positions and the same 270-degree focus throw. That means no rig rebuild when you change focal lengths.

What is the minimum focus distance?

About 0.26m on the 24mm, 0.3m on the 35mm and 0.43m on the 50mm. The wide lenses get close enough for detail inserts; the 50mm is more of a standard working distance.

Will these cover a full-frame sensor?

Yes. The image circle is 46mm, which covers full-frame and leaves headroom for some stabilization or slight reframing. They also work on Super 35 bodies with a tighter crop.

What comes in the set?

Three lenses (24mm, 35mm, 50mm), each with its chosen mount, front and rear caps, and a hard case. Check the mount you pick at checkout, since it is not universal out of the box.