I have examined your questions and come to the following conclusions:
(1)The ODR in our factory Units is 50hz.
(2)The setting of Units with SN:1974001265 may have been changed.
(3)In future, the default configurations of Units are:
FW2.1, baudrate:115200, output rate:50hz, packet type: z1

I will check the factory Settings of these two Units, when i find the difference between both of them, I will reply you.

You can use "pG" command "55 55 70 47 00 5D 5F" to get device serial number, firmware version and factory ID.

At the same time please follow below steps to set output data rate(ODR)200hz permanently:
"uP" command: "55 55 75 50 0C 04 00 00 00 C8 00 00 00 00 00 00 00 F0 D5" ，set ODR 200HZ.
"uP" command feedback "55 55 75 50 04 00 00 00 00 1C 26", it means operation succeeded.
"sC" command "55 55 73 43 00 C8 CB" , save the parameters.

The factory firmware_1.1.10 of the OpenIMU330 does not support 200hz output updates.
Please upgrade the firmware of your device by SWD interface with ST-LINK, for detail steps about the upgrade process, see the link:
https://forum.aceinna.com/topic/93/top-topics-of-common-operations-with-openimu-products.
"9. how to upgrade only new FW with ST-LINK?"
"for 330"

The attached firmware is a latest version that supports 200 Hz output, so you can try to use it .
OpenIMU330BI_FW02.01.bin