Can a ball valve throttle?

V-port or characterized balls can; standard balls are for on-off.

When must I use globe?

Frequent modulation and precise Cv control usually stay with globe/control valves.

Throttling needs differ from on-off isolation. Globe and ball are not interchangeable without checking the datasheet.

Topic	Globe	Ball
Primary use	Throttling / regulating	On-off (some characterized balls)
Pressure drop	Higher	Lower when full open
Stem seal	Packing / bellows options	Packing / stem seals
RFQ cue	Trim + Cv	Floating/trunnion + seat
Fire safe	As specified	Common ask on hydrocarbon

If the P&ID shows control duty, send Cv, signal, and fail position — not only valve type.