Upper back development can be considered a lot more complex due to the fact that it is comprised of multiple different muscles. But, according to evidence based peer-review research, one of the top exercises for upper back development is chest supported rows.

Keep in mind, focus on a wider grip, elbow flared position while performing the chest supported row. The closer your elbows are to your ribcage, the less activated the upper back becomes. 

EMG studies consistently show high activation of the rhomboids, middle trapezius, and rear delts. This movement can be performed on a machine, t-bar, or with free weight. 

The chest supported row is considered highly effective due to the fact that you minimize momentum. While specific electromyographic (EMG) studies directly comparing chest-supported rows to other rowing exercises are limited, the chest-supported position is noted to reduce lower back involvement, potentially allowing for greater isolation & activation of the upper back muscles.

Bent-over rows have been known to engage the lower back & hamstrings (especially @ heavier loads) due to the need for torso stabilization. This can lead to increased fatigue and potentially limit the focus on the upper back musculature. Therefore, chest-supported rows may be advantageous for individuals aiming to concentrate & develop upper back musculature without additional lower back strain. But, statistics do show that versions of bent over rows can be beneficial to integrate into a training regimen as well. 

Personally & anecdotally, I would recommend combining various rowing techniques within your phases training program. This can help provide comprehensive back development by engaging multiple different muscle groups & importance 

Peer reviewed studies:

Surface electromyographic analysis of exercises for the trapezius and serratus anterior muscles

https://pubmed.ncbi.nlm.nih.gov/12774999/

Schoenfeld et al. (2010) – emphasized the importance of rowing variations for upper back development.

A study published in the Journal of Strength and Conditioning Research compared muscle activation during seated rows and lat pulldowns. The findings indicated that seated rows elicited higher activation in the middle trapezius and rhomboids compared to lat pulldowns, suggesting their superiority for upper back development. https://pmc.ncbi.nlm.nih.gov/articles/PMC449729/?utm_

Research in the International Journal of Strength and Conditioning examined how different grip positions and shoulder abduction angles affect muscle activation during seated cable rows. https://www.researchgate.net/publication/371114847_Effect_Of_Different_Grip_Position_And_Shoulder-_Abduction_Angle_On_Muscle_Strength_And_Activation_During_The_Seated_Cable_Row?utm_

The study found that a supinated grip and a 60° shoulder abduction angle significantly increased activation of the latissimus dorsi and biceps brachii, enhancing the effectiveness of the exercise for upper back hypertrophy. https://pmc.ncbi.nlm.nih.gov/articles/PMC449729/?utm_

An investigation into various rowing exercises, including inverted rows, standing bent-over rows, and one-armed cable rows, revealed that inverted rows produced the highest muscle activation in the upper back muscles. This suggests that inverted rows may be particularly beneficial for targeting the upper back. chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https://www.backfitpro.com/medical-scientific-articles/2009/%5B80%5DFenwick%2CC.M.J.%282009%29Comparison-of-different-rowing-exercises%5BJ.Strength-and-Cond.%5D.pdf?utm_

Effect of grip width on electromyographic activity during the upright row https://pubmed.ncbi.nlm.nih.gov/22362088/

ELECTROMYOGRAPHIC ANALYSIS OF THE BACK DURING VARIOUS BACK EXERCISES 

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Int. J. Strength Cond.[PDF] Effect Of Different Grip Position And Shoulder- Abduction Angle On ...The seated cable row is a multi-joint exercise widely used to increase strength and hypertrophy of the upper and lower back, and elbow flexors [1-3]. In.