We now look at the fielding figures for Test captains. This includes both keepers and non-keepers.
Most dismissals (35 and above):

Led by Dhoni (211) followed by non-keepers GC Smith (152) and Fleming (132) and current keeper Paine (101)
Fine-tuning:
A Flower and AJ Stewart had captained both as keepers and as non-keepers. Sangakkara and AB de Villiers never captained as a keeper.
Most catches by WK: 187 by Dhoni, almost double the next (97 by Paine).
Most stumpings: 24 by Dhoni, followed by Sherwell (16 from long ago)
Most catches by non-keeper: 152 by GC Smith, 132 by Fleming. The highest for India is 59 by Kohli
Most dismissals in an innings (5 and above):

Rashid Latif and Dhoni have the most dismissals (6).
Among non-keepers, the highest is 5 by VY Richardson, Fleming, GC Smith, Sammy and SPD Smith.
5 is still the world record for catches by a fielder in an innings. It is shared by several others. VY Richardson was the first to achieve this. He is better known as the (maternal) grandfather of the Chappells.
Most dismissals in a match (7 and above):

Here the record is 10 by Sarfaraz Ahmed, who had a relatively short spell as captain.
For non-keepers, it is 7 by Fleming. This was a share in the world record until AM Rahane took 8 catches.
And the most stumpings appear to be 3 by Dhoni in 2010.
Highest dismissal rate (Minimum 20 innings, and 0.65):

Here the results are a little surprising: Paine (2.244) followed by Sarfaraz (2.200) and Alexander. Dhoni is next.
Among fielders, the leader is SPD Smith(1.187) followed by DJG Sammy (1.075). Dravid (0.702) has the most for India.
You may also like to see this, which has the same dateline in May 2021.