2021 had relatively fewer ODIs than in recent years. Covid cancellations played their part, and many teams gave priority to T20Is because of the World Cup late in the year. (But that will happen in 2022 as well). Anyway, we summarize whatever information is available for ODIs in the calendar year 2021.
Team performances:

Considering teams which have played at least 10 matches, the best W/L ratios are by Bangladesh and Oman followed by South Africa. Teams such as New Zealand, England, Australia and India played less than 10 matches.
Batting:
Most runs (250 and above):

As you may guess, the most runs were played by someone from a minor team: PR Stirling of Ireland with 706. Next is JN Malan of SA with 509. India has one representative here in S Dhawan (297).
The most centuries are 3 by PR Stirling, and 2 by 3 others.
The most 50+ scores are 5 by Stirling (again) and Tamim Iqbal.
Highest individual scores (100 and above):

The top scores (above 150) are 193 by Fakhar Zaman, 177* by JN Malan, 173* by JS Malhotra (USA) and 158 by Babar Azam. The best for India is 108 by KL Rahul.
There is not enough data (minimum 20 innings) for batting averages. However, we have something for Strike Rates (Minimum 500 balls faced, all instances):

JN Malan’s 90+ SR is considerably higher than the next (Stirling yet again).
To be continued.