And some data from my side:
Without a limit
etexter@seraphite ~ % rclone size DB: -vvv
2021/12/08 07:24:40 DEBUG : rclone: Version "v1.57.0" starting with parameters ["rclone" "size" "DB:" "-vvv"]
2021/12/08 07:24:40 DEBUG : Creating backend with remote "DB:"
2021/12/08 07:24:40 DEBUG : Using config file from "/Users/etexter/.config/rclone/rclone.conf"
2021/12/08 07:26:26 NOTICE: too_many_requests/.: Too many requests or write operations. Trying again in 300 seconds.
2021/12/08 07:26:26 DEBUG : pacer: low level retry 1/10 (error too_many_requests/.)
2021/12/08 07:26:26 DEBUG : pacer: Rate limited, increasing sleep to 5m0s
2021/12/08 07:26:26 DEBUG : pacer: Reducing sleep to 3m45s
2021/12/08 07:26:26 NOTICE: too_many_requests/.: Too many requests or write operations. Trying again in 300 seconds.
2021/12/08 07:26:26 DEBUG : pacer: low level retry 1/10 (error too_many_requests/.)
2021/12/08 07:26:26 DEBUG : pacer: Rate limited, increasing sleep to 5m0s
2021/12/08 07:26:26 NOTICE: too_many_requests/..: Too many requests or write operations. Trying again in 300 seconds.
2021/12/08 07:26:26 DEBUG : pacer: low level retry 1/10 (error too_many_requests/..)
2021/12/08 07:26:26 DEBUG : pacer: Reducing sleep to 3m45s
2021/12/08 07:26:26 DEBUG : pacer: Reducing sleep to 2m48.75s
2021/12/08 07:26:26 NOTICE: too_many_requests/.: Too many requests or write operations. Trying again in 300 seconds.
2021/12/08 07:26:26 DEBUG : pacer: low level retry 2/10 (error too_many_requests/.)
2021/12/08 07:26:26 DEBUG : pacer: Rate limited, increasing sleep to 5m0s
2021/12/08 07:26:26 DEBUG : pacer: Reducing sleep to 3m45s
2021/12/08 07:26:26 DEBUG : pacer: Reducing sleep to 2m48.75s
^C2021/12/08 07:26:34 INFO : Signal received: interrupt
2021/12/08 07:26:34 INFO : Dropbox root '': Commiting uploads - please wait...
2021/12/08 07:26:34 INFO : Exiting...
With a limit
etexter@seraphite ~ % rclone size DB: -vvv --tpslimit 12 --tpslimit-burst 12
2021/12/08 07:48:33 INFO : Starting transaction limiter: max 12 transactions/s with burst 12
2021/12/08 07:48:33 DEBUG : rclone: Version "v1.57.0" starting with parameters ["rclone" "size" "DB:" "-vvv" "--tpslimit" "12" "--tpslimit-burst" "12"]
2021/12/08 07:48:33 DEBUG : Creating backend with remote "DB:"
2021/12/08 07:48:33 DEBUG : Using config file from "/Users/etexter/.config/rclone/rclone.conf"
Total objects: 55.699k (55699)
Total size: 180.908 TiB (198910637106946 Byte)
2021/12/08 07:56:26 DEBUG : 7 go routines active
2021/12/08 07:56:26 INFO : Dropbox root '': Commiting uploads - please wait...