Efficiency or longevity issues when using 2 lamps on a 4-lamp fluorescent ballast?
Fluorescent tubes consume current generally according to the diameter of the tube and length while longer tubes require a higher trigger voltage after which they function Lower voltage from negative resistance.
Modern  ballasts did not require a pre-heater for the tubes and both pins are shorted together. Universal ballasts are capable of triggering both T8’s and T12’s and are independent of the number of tubes energized.
Although not as efficient as LEDs with 125 to 150 lm per watt modern fluorescent tubes that are true daylight have triple phosphors to convert ultraviolet into three colour bands that gives a more pleasant colour than LEDs‘(IMHO). CRI is not the best indicator for FL vs LED’s as they have a broader spectrum.
These come in a variety of colour temperatures 5000° K for true daylight, 4100 ° K, Instead of the dual phosphor warm or cold.  89 l/w 20kh rated yet 50kh if used all the time, meaning starts reduce MTBF hrs.
F32T8/TL941 Philips are Tri-phosphor Lamps 4100° K 32W. There also exist higher efficiency types of 30, 28W but only on custom order per box of 10. TL950 would be 5000° K.
I have made my own fixtures just using the “tombstone” connectors in recessed lighting with one wire to each end (yellow being common).